Lithium Ion Batteries with Supplemental Lithium

ABSTRACT

Supplemental lithium can be used to stabilize lithium ion batteries with lithium rich metal oxides as the positive electrode active material. Dramatic improvements in the specific capacity at long cycling have been obtained. The supplemental lithium can be provided with the negative electrode, or alternatively as a sacrificial material that is subsequently driven into the negative electrode active material. The supplemental lithium can be provided to the negative electrode active material prior to assembly of the battery using electrochemical deposition. The positive electrode active materials can comprise a layered-layered structure comprising manganese as well as nickel and/or cobalt.

FIELD OF THE INVENTION

The invention relates to lithium-based batteries having a positiveelectrode active material, such as a lithium rich composition, and anegative electrode active material that can intercalate/alloy withlithium during charging, in which the battery is formed with additionallabile or extractable lithium in addition to the removable lithiumprovided by the positive electrode active material. The inventionfurther relates to high voltage lithium secondary batteries withsurprisingly excellent cycling at very high specific capacities.

BACKGROUND OF THE INVENTION

Lithium batteries are widely used in consumer electronics due to theirrelatively high energy density. Rechargeable batteries are also referredto as secondary batteries, and lithium ion secondary batteries generallyhave a negative electrode material that intercalates lithium or alloyswith lithium. For some current commercial batteries, the negativeelectrode material can be graphite, and the positive electrode materialcan comprise lithium cobalt oxide (LiCoO₂). In practice, only a modestportion of the theoretical capacity of the cathode can be used. At leasttwo other lithium-based cathode materials are also currently incommercial use. These two materials are LiMn₂O₄, having a spinelstructure, and LiFePO₄, having an olivine structure. These othermaterials have not provided any significant improvements in energydensity.

Lithium ion batteries are generally classified into two categories basedon their application. The first category involves high power batteries,whereby lithium ion battery cells are designed to deliver high current(Amperes) for such applications as power tools and Hybrid ElectricVehicles (HEVs). However, by design, these battery cells are lower inenergy since a design providing for high current generally reduces totalenergy that can be delivered from the battery. The second designcategory involves high energy batteries, whereby lithium ion batterycells are designed to deliver low to moderate current (Amperes) for suchapplications as cellular phones, lap-top computers, Electric Vehicles(EVs) and Plug in Hybrid Electric Vehicles (PHEVs) with the delivery ofhigher total capacity.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to a lithium ion batterycomprising supplemental lithium, a positive electrode, a negativeelectrode, a separator between the positive electrode and the negativeelectrode and an electrolyte comprising lithium ions. In someembodiments, the negative electrode comprising a lithiumintercalation/alloying composition, and the positive electrode comprisesa composition approximately represented by a formulaLi_(1+x)M_(1−y)O_(2−z)F_(z) where M is one or more metal elements, x isfrom about 0.01 to about 0.33, y is from about x−0.2 to about x+0.2 withthe proviso that y≧0, and z is from 0 to about 0.2.

In a further aspect, the invention pertains to a lithium ion batterycomprising a negative electrode comprising a lithium intercalationcomposition, a positive electrode comprising Li_(1+x)M_(1−y)O_(2−z)F_(z)where M is one or more metal elements, x is from about 0.01 to about0.33, y is from about x−0.2 to about x+0.2 with the proviso that y≧0,and z is from 0 to about 0.2, and a separator between the negativeelectrode and the positive electrode. After 600 cycles between 4.5V and2.0V, the negative electrode can comprise no more than about 1 weightpercent metals from the positive electrode.

In another aspect, the invention pertains to a lithium ion batterycomprising a positive electrode, a negative electrode, a separatorbetween the positive electrode and the negative electrode and anelectrolyte comprising lithium ions, the negative electrode comprising alithium intercalation/alloying composition. The positive electrode cancomprise a composition approximately represented by a formulaLi_(1+x)M_(1−y)O_(2−z)F_(z) where M is one or more metal elements, x isfrom about 0.01 to about 0.33, y is from about x−0.2 to about x+0.2 withthe proviso that y≧0, and z is from 0 to about 0.2. In some embodiments,after cycling the battery for 20 cycles from 4.5 volts to 2 volts andafter discharging the battery to 98% of the discharge capacity, thenegative electrode can be removed and electrochemicallyde-intercalated/de-alloyed with a capacity of at least about 0.5% of thenegative electrode capacity with the corresponding removal of lithiumfrom the negative electrode.

In other aspects, the claimed invention pertains to a lithium ionbattery comprising a positive electrode, a negative electrode, aseparator between the positive electrode and the negative electrode andan electrolyte comprising lithium ions, the negative electrodecomprising a lithium intercalation/alloying composition, in which thepositive electrode has a room temperature specific discharge capacity atthe 200th cycle that is at least about 92.5% of the 5th cycle specificdischarge capacity when discharged from the 5th cycle to the 200th cycleat a C/3 rate from 4.5V to 2V.

Moreover, the invention pertains to a lithium ion battery comprising apositive electrode, a negative electrode, a separator between thepositive electrode and the negative electrode and an electrolytecomprising lithium ions, the negative electrode comprising a lithiumintercalation/alloying composition, in which the battery has a roomtemperature specific discharge capacity at the 175th cycle that is atleast about 75% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 175th cycle at a 1 C rate from 4.5Vto 2V.

In addition, the invention pertains to a lithium ion battery comprisinga positive electrode, a negative electrode, a separator between thepositive electrode and the negative electrode and an electrolytecomprising lithium ions, the negative electrode comprising a lithiumintercalation/alloying composition, wherein the battery has a specificdischarge capacity at the 45th cycle that is at least about 90% of the5th cycle specific discharge capacity when discharged from the 5th cycleto the 45th cycle at a C/3 rate from 4.5V to 2V at a temperature of 55°C.

Furthermore, the invention pertains to a method for the formation of anegative electrode for a lithium ion battery wherein the negativeelectrode comprises an active lithium intercalation/alloying compositionand a polymer binder, the method comprising:

electrochemically intercalation/alloying lithium into the activecomposition;

de-intercalating/de-alloying electrochemically the lithium from theactive composition;

partially electrochemically intercalating/alloying the lithiumintercalation/alloying composition to a level from about 2 percent toabout 75 percent of the capacity of the composition.

In some embodiments, the electrochemical intercalation/alloying stepcomprises the intercalation/alloying of lithium to a level of at leastabout 80 percent of theoretical capacity of the composition and the stepof de-intercalating/de-alloying of lithium to a state of the activematerial with lithium in an amount of no more than about 25% ofcapacity.

Additionally, the invention pertains to a method for forming a lithiumion battery with supplemental lithium stored in the negative electrodewherein the negative electrode comprises a lithiumintercalation/alloying composition and a polymer binder, the methodcomprising the step of closing a circuit to load supplemental lithiumfrom a sacrificial lithium source into the lithiumintercalation/alloying composition in the negative electrode.

Also, the invention pertains to a lithium ion battery comprising anegative electrode comprising a lithium intercalation composition, apositive electrode comprising Li_(1+x)M_(1−y)O_(2−z)F_(z) where M is oneor more metal elements, x is from about 0.01 to about 0.33, y is fromabout x−0.2 to about x+0.2 with the proviso that y≧0, and z is from 0 toabout 0.2; and a separator between the negative electrode and thepositive electrode, in which from about 300 cycles to about 600 cyclesthe positive electrode active material has a specific discharge capacityof at least about 90 mAh/g between 3V and 2.5V.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a battery stack with a cathodeand anode and a separator between the cathode and anode.

FIG. 2 is schematic side view of an electrode stack with an optionalsacrificial electrode and optional supplemental lithium within thecathode, i.e. positive electrode.

FIG. 3 is a schematic side view of an anode, i.e., negative electrode,on a current collector in which the negative electrode comprises asupplemental lithium source within the body of the electrode.

FIG. 4A is a schematic side view of a negative electrode on a currentcollector in which the negative electrode comprises a layer ofsupplemental lithium on the surface of the negative electrode.

FIG. 4B is a schematic side view of a negative electrode on a currentcollector in which the negative electrode comprises a layer ofsupplemental lithium between the negative electrode and the currentcollector.

FIG. 5 is a schematic side view of a negative electrode on a currentcollector in which the negative electrode active material is partiallylithiated.

FIG. 6 is a schematic view of a vessel with electrolyte holding anegative electrode with a sheet of lithium source material contactingthe negative electrode to perform lithiation of the negative electrode.

FIG. 7 is a schematic view of a vessel with electrolyte and a cellcomprising an electrode to be lithiated and a lithium source electrodeseparated with a separator and connected through an external circuit, inwhich the electrode to be lithiated will subsequently be used as anegative electrode in a final battery.

FIG. 8 is a graph comparing plots of specific discharge capacity versuscycle number for batteries with and without supplemental lithium andformed from positive electrode active materials wherein X=0.5.

FIG. 9 is a graph comparing plots of specific discharge capacity versuscycle number for batteries with and without supplemental lithium formedfrom positive electrode active materials wherein X=0.3.

FIG. 10 is a graph comparing plots of specific discharge capacity versuscycle number for batteries with and without supplemental lithium cycledwith a charge/discharge rate of 1 C.

FIG. 11 is a graph comparing plots of specific discharge capacity versuscycle number for batteries with and without supplemental lithium cycledat a temperature of 55° C.

FIG. 12 is a graph comparing plots of discharge voltage versusaccumulated discharge capacity for batteries with and withoutsupplemental lithium at various cycle numbers.

FIG. 13 is a graph comparing plots of specific discharge capacity versuscycle number for batteries balanced at 107% anode and comprising variousamounts of supplemental lithium.

FIG. 14 is a graph comparing plots of specific discharge capacity versuscycle number for batteries balanced at 120% anode and comprising variousamounts of supplemental lithium.

FIG. 15 is a graph comparing histograms of specific discharge capacityversus amount of supplemental lithium for batteries balanced at 106%,120% and 140% anode.

FIG. 16 is a graph comparing plots of charging voltage versus chargingcapacity for test coin-cells formed from positive electrodes obtainedfrom cycled batteries with and without supplemental lithium.

FIG. 17 is a graph comparing normalized heat flow versus temperature forlithiated and non-lithiated graphitic electrodes obtained bydifferential scanning calorimetry.

FIG. 18 is a high resolution transmission electron microscopy image of apositive electrode taken after long cycling from a battery withoutsupplemental lithium.

FIG. 19 is a high resolution transmission electron microscopy image of apositive electrode taken after long cycling form a battery withsupplemental lithium.

FIG. 20 is a composite of electron diffraction patterns obtained fromelectron diffraction spectroscopy measurements of positive electrodestaken, after cycling, from batteries with (right panel) and without(left panel) supplemental lithium.

FIG. 21 is a graph comparing plots of differential capacity versusvoltage at various cycle numbers for a battery without supplementallithium.

FIG. 22 is a graph comparing plots of differential capacity versusvoltage at various cycle numbers for batteries with and withoutsupplemental lithium.

FIG. 23 is a graph comparing plots of ionic contributions to thespecific capacity versus voltage at various cycle numbers for batterieswith and without supplemental lithium.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that the addition of a supplemental lithiumsource for a lithium ion battery with a lithium intercalation/alloyingcomposition in the negative electrode results in dramatic decrease inthe fading of specific capacity of the positive electrode activematerial, e.g., a lithium rich metal oxide, upon cycling. This decreasein fading has been identified with stabilization of the positiveelectrode active material with a corresponding decrease in transitionmetal dissolution into the electrolyte and incorporation into thenegative electrode active material. The positive electrode activematerial can be a lithium rich positive electrode active material, suchas materials represented by the formula x Li₂M′O₃.(1−x) LiMO₂, where Mrepresents one or more metal elements with an average valance of +3 andM′ represents one or more metal elements with an average valance of +4.The significantly improved cycling is surprisingly observed with lithiumrich positive electrode active materials, which can be expected tosupply some excess lithium to the negative electrode in the initialcharge that is not cycled due to irreversible changes to the positiveelectrode active materials. The formation of a more stable solidelectrolyte interphase layer has also been observed. Based on the use ofthe lithium rich positive electrode active materials with thesupplemental lithium, the corresponding batteries can cycle with highcapacities for a large number of cycles with significantly reducedfading of the battery capacities.

The supplemental lithium can be provided to the negative electrode invarious ways. In particular suitable approaches include, for example,introducing elemental lithium into the battery, the incorporation of asacrificial material with active lithium that can be transferred to thenegative electrode active material, or preloading of lithium into thenegative electrode active material. A lithium source material can beassociated initially with the negative electrode, the positive electrodeand/or a sacrificial electrode. If the lithium source material isinitially associated with the positive electrode or a sacrificialelectrode, the supplemental lithium generally is associated with thenegative electrode active material after the first charge step, althougha portion of the lithium can be associated with irreversible reactionbyproducts, such as the solid electrolyte interphase layer.

Lithium has been used in both primary and secondary batteries. Anattractive feature of lithium metal for battery use is its light weightand the fact that it is the most electropositive metal, and aspects ofthese features can be advantageously captured in lithium-based batteriesalso. Certain forms of metals, metal oxides, and carbon materials areknown to incorporate lithium ions into its structure throughintercalation, alloying or similar mechanisms. Lithium ion batterieshave generally referred to batteries in which the negative electrodeactive material is also a lithium intercalation/alloying material.Desirable lithium rich mixed metal oxides are described further hereinto function as electroactive materials for positive electrodes insecondary lithium ion batteries.

If elemental lithium metal itself is used as the anode or negativeelectroactive material, the resulting battery generally is referred toas a lithium battery. Lithium batteries can initially cycle with goodperformance, but dendrites can form upon lithium metal deposition thateventually can breach the separator and result in failure of thebattery. As a result, commercial lithium-based secondary batteries havegenerally avoided the deposition of lithium metal through the use of anegative electrode active material that operates throughintercalation/alloying or the like with a slight excess in negativeelectrode capacity relative to the positive electrode. In other words,appropriately designed lithium ion batteries generally avoid theformation of lithium dendrites.

The batteries described herein are lithium-based batteries in which anon-aqueous electrolyte solution comprises lithium ions. For secondarylithium ion batteries during charge, oxidation takes place in thecathode (positive electrode) where lithium ions are extracted andelectrons are released. During discharge, reduction takes place in thecathode where lithium ions are inserted and electrons are consumed.Unless indicated otherwise, performance values referenced herein are atroom temperature.

The word “element” is used herein in its conventional way as referringto a member of the periodic table in which the element has theappropriate oxidation state if the element is in a composition and inwhich the element is in its elemental form, M⁰, only when stated to bein an elemental form. Therefore, a metal element generally is only in ametallic state in its elemental form or a corresponding alloy of themetal's elemental form. In other words, a metal oxide or other metalcomposition, other than metal alloys, generally is not metallic.

When lithium ion batteries are in use, the uptake and release of lithiumfrom the positive electrode and the negative electrode induces changesin the structure of the electroactive material. As long as these changesare essentially reversible, the capacity of the material does notchange. However, the capacity of the active materials is observed todecrease with cycling to varying degrees. Thus, after a number ofcycles, the performance of the battery falls below acceptable values,and the battery is replaced. Also, on the first cycle of the battery,generally there is an irreversible capacity loss that is significantlygreater than per cycle capacity loss at subsequent cycles. Theirreversible capacity loss is the difference between the charge capacityof the new battery and the first discharge capacity. The irreversiblecapacity loss results in a corresponding decrease in the capacity,energy and power for the cell due to changes in the battery materialsduring the initial cycle.

In lithium ion batteries, the active lithium is generally initiallysupplied with the positive electrode active material. Specifically, thecathode material generally is initially a lithium metal oxide, such thatthe battery is first charged to extract the lithium from the positiveelectrode for transfer to the negative electrode where the lithium isthen available for discharging of the battery. During an initial chargeof the battery, labile lithium leaves from the positive electrode activematerial and is taken up reversibly by the negative electrode activematerial, although some of the lithium may be consumed by irreversiblereactions within the battery. The batteries of particular interestcomprise an initial supplemental amount of active lithium in addition tothe reactive lithium supplied with the positive electrode activematerial. Surprisingly, the supplemental lithium source providesdramatic improvement to the cycling performance of batteries having alithium rich positive electrode active material. In particular, thissupplemental lithium is surprisingly able to stabilize the positiveelectrode active material with respect to the degradation of thepositive electrode active material. The examples below provide evidenceregarding the stabilization of the positive electrode active materials.Data presented in the Examples also indicates that the initially formedsolid electrolyte interphase layer is more stable for batteries withsupplemental lithium along with the lithium rich positive electrodeactive material.

Generally, during the first charge of a lithium ion battery, graphiticcarbon or other active material reacts at its surface with theelectrolyte to form a solid electrolyte interphase (SEI) layer as acoating on the active negative electrode materials, which is believed tocomprise some lithium that is consumed from the available lithiumaccessible for cycling. Other negative electrode active materials thattake up lithium through intercalation, alloying or the like generallyalso react during an initial charge to form an SEI layer. The SEI layercan comprise a by-product of the breakdown of the electrolyte that isbelieved to incorporate lithium ions into the layer. Thus, the SEI layergenerally irreversibly consumes some of the lithium released from thepositive electrode during the initial charge of the battery or from asupplemental lithium source. The SEI layer is believed to stabilize thecycling of the battery and to reduce or eliminate the further reactionof the electrolyte at the negative electrode active material.

It has been found that lithium rich positive electrode materials providevery high cycling discharge capacities and good cycling properties underappropriate circumstances. However, for the lithium rich compositionsdescribed herein, significant structural and/or compositional changestake place with respect to the positive electrode active material duringthe first charge, and the changes to the positive electrode activematerial can contribute significantly to the irreversible capacity loss.In some embodiments, for batteries with lithium rich positive electrodeactive materials, the irreversible capacity loss associated with thepositive electrode active material can be significantly greater than theirreversible capacity loss associated with formation of the solidelectrolyte interphase layer.

Based on an initial lithium rich material, the resulting metal oxidefollowing the initial charge generally is incapable of incorporating allof the lithium released back into the material. So the lithium richmetal oxides also can supply excess lithium relative to the amount oflithium cycled. This excess lithium from irreversible changes to thelithium rich metal oxides is confirmed in the data presented in theExamples below. Some of the excess lithium from the irreversible changesto the positive electrode active material may be deposited in the formof lithium oxide, which is inert during cycling, in the SEI layer at thenegative electrode and/or in the structure of the negative electrodeactive material where it is available for cycling but not used forcycling.

Thus, it is particularly surprising and particularly significant thatthe addition of supplemental lithium in batteries improved performancewith a lithium rich positive electrode active material sinceirreversible changes to the positive electrode active material alreadysupplies additional lithium to the battery relative to the cyclingcapacity. Any excess lithium resulting from the irreversible changes tothe positive electrode active material is in addition to thesupplemental lithium described herein. The positive electrode lithiumrich compositions can be charged to voltages above 4.3 V such that theyexhibit a high specific capacity. In particular, if the performance ofboth the positive electrode and negative electrode are stable and canachieve a high specific capacity, superior battery performance can beachieved over a large number of cycles.

The first cycle of the battery can be considered a formation cycle dueto the irreversible changes that occur. With the addition ofsupplemental lithium, the negative electrode active material is loadedwith significant amounts of excess lithium following discharge of thebattery after the first cycle. Depending on the approach to add thesupplemental lithium, this lithium can be incorporated into the negativeelectrode active material spontaneously or the added lithium isincorporated into the negative electrode with the passage of currentthrough an external circuit, either with or without the addition of avoltage, depending on the source of the supplemental lithium.

As the battery is cycled, the supplemental lithium can be identified inthe negative electrode following the discharge of the battery. Duringdischarge, lithium is returned to the positive electrode and depletedfrom the negative electrode. Some lithium can remain in the negativeelectrode after discharge possibly due to the irreversible capacity lossin the formation cycle. However, when supplemental lithium has beenadded to the battery, a significantly larger amount of lithium is foundin the negative electrode following discharge of the battery. Asdescribed in more detail below, the presence of remaining lithium in thenegative electrode can be measured by discharging the battery, removingthe negative electrode and further removing lithium(de-intercalating/de-alloying) from the negative electrode afterremoval. The qualitatively different performance of the battery observedif supplemental lithium is added is observed even though there is asmall amount of remaining lithium in the negative electrode upondischarge even if the supplemental lithium is not added to the battery.Thus, even though there is some extra lithium from the irreversiblecapacity loss of the positive electrode active material, there is adramatic change in the performance if additional supplemental lithium inincorporated into the battery.

The results presented herein demonstrate that the battery can losecapacity with cycling at least in part due to dissolution of transitionmetals from the positive electrode active materials. For reasons thatare not understood, if supplemental active lithium is provided to thenegative electrode, this dissolution of transition metals from thepositive electrode is decreased to a very large degree. Thus,measurements of the decrease in transition metal dissolution withcycling can be used to evaluate the initial presence of supplementallithium. Also, in some embodiments, stable discharge capacity between 3Vand 2.5V grows in with cycling that continues out to relatively largecycle numbers.

As described herein, positive electrode compositions can include, forexample, lithium rich metal oxides, which can operate at relatively highvoltages and, in some embodiments, may have a specific layered-layeredcomposite structure. The positive electrode compositions can be coatedto stabilize further the composition for cycling at high voltages with acorresponding high specific capacity. With the addition of supplementallithium, the high specific capacities of the coated positive electrodeactive materials can be essentially maintained with little or nocapacity fade over a large number of charge/discharge cycles under highvoltage operation. The materials can also exhibit good performance athigher rates while still maintaining a low capacity fade, e.g. highcoulombic efficiency.

The lithium ion batteries can use a positive electrode active materialthat is lithium rich relative to a reference homogenous electroactivelithium metal oxide composition. In general, the lithium richcompositions of interest can be approximately represented by the formulaLi_(1+b)Mn_(β)M_(1−b−β)O_(2−z)F_(z), where M is one or more metalelements, b is from about 0.01 to about 0.33, β is from about 0.3 toabout 0.65, and z is from 0 to about 0.2. Fluorine is an optional aniondopant. This composition is lithium rich relative to referencecomposition with the formula LiMO₂.

In some embodiments, it is believed that appropriately formedlithium-rich lithium metal oxides have a composite crystal structure.For example, in some embodiments of lithium rich materials, a layeredLi₂M′O₃ material may be structurally integrated with a layered LiMO₂component, in which a reference structure has M and M′ being manganese,although particular compositions of interest have a portion of themanganese cations substituted with other transition metal cations withappropriate oxidation states. M is one or more metal cations with anaverage valance of +3, and M′ is one or more metal cations with anaverage valance of +4. Generally, for compositions of particularinterest, M′ can be considered to be Mn. The general class ofcompositions are described further, for example, in U.S. Pat. No.6,680,143 (the '143 patent) to Thackeray et al., entitled “Lithium MetalOxide Electrodes for Lithium Cells and Batteries,” incorporated hereinby reference.

In some embodiments, the class of lithium rich positive electrode activematerials can be approximately represented with a formula:

Li_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O_(2−z)F_(z),  (1)

where b ranges from about 0.01 to about 0.3, α ranges from 0 to about0.4, β range from about 0.2 to about 0.65, γ ranges from about 0 toabout 0.46, δ ranges from about 0 to about 0.15, and z ranges from 0 toabout 0.2 with the proviso that both α and γ are not zero, and where Ais a metal element different from Ni, Mn and Co or a combinationthereof. Element A and F (fluorine) are optional cation and aniondopants, respectively. Element A can be, for example, Mg, Sr, Ba, Cd,Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinationsthereof. The use of a fluorine dopant in lithium rich metal oxides toachieve improved performance is described in copending U.S. patentapplication Ser. No. 12/569,606 to Kumar et al., entitled “FluorineDoped Lithium Rich Metal Oxide Positive Electrode Battery Materials WithHigh Specific Capacity and Corresponding Batteries,” incorporated hereinby reference.

The formulas presented herein for the positive electrode activematerials are based on the molar quantities of starting materials in thesynthesis, which can be accurately determined. With respect to themultiple metal cations, these are generally believed to bequantitatively incorporated into the final material with no knownsignificant pathway resulting in the loss of the metals from the productcompositions. Of course, many of the metals have multiple oxidationstates, which are related to their activity with respect to thebatteries. Due to the presence of the multiple oxidation states andmultiple metals, the precise stoichiometry with respect to oxygengenerally is only roughly estimated based on the crystal structure,electrochemical performance and proportions of reactant metals, as isconventional in the art. However, based on the crystal structure, theoverall stoichiometry with respect to the oxygen is reasonablyestimated. All of the protocols discussed in this paragraph and relatedissues herein are routine in the art and are the long establishedapproaches with respect to these issues in the field.

The stoichiometric selection for the compositions can be based on somepresumed relationships of the oxidation states of the metal ions in thecomposition. As an initial matter, if in Eq. (1) approximatelyb+α+β+γ+δ=1, then the formula of the composition can be correspondinglyapproximately written in two component notation as:

x.Li₂MnO₃.(1−x)LiM′O₂,  (2)

where M′ is one or more metal atoms with an average oxidation state of+3. In some embodiments, M′ comprises manganese, nickel, cobalt or acombination thereof along with an optional dopant metal. Then, the twocomponent notation becomes x.Li₂MnO₃.(1−x)LiNi_(u)Mn_(v)Co_(w)A_(y)O₂,where u+v+w+y≈1. While Mn, Co and Ni have multiple accessible oxidationstates, which directly relates to their use in the active material, inthese composite materials if appropriate amounts of these elements arepresent, it is thought that the elements can have the oxidation statesMn⁺⁴, Co⁺³ and Ni⁺². Then, if δ=0 in Eq. (1), the two component notationcan simplify with v≈u to x.Li₂MnO₃.(1−x)LiNi_(u)Mn_(u)Co_(w)O₂, with2u+w=1. In some embodiments, the stoichiometric selection of the metalelements can be based on these presumed oxidation states. Based on theoxidation state of dopant element A, corresponding modifications of theformula can be made. Also, compositions can be consider in which thecomposition varies around the stoichiometry with v≈u, and thesecompositions are described in detail in copending U.S. patentapplication Ser. No. 12/869,976 (the '976 application) to Lopez et al.,entitled “Layer-Layer Lithium Rich Complex Metal Oxides With HighSpecific Capacity and Excellent Cycling,” incorporated herein byreference. Similar compositions have been described in published U.S.patent application 2010/0086853A (the '853 application) to Venkatachalamet al. entitled “Positive Electrode Material for Lithium Ion BatteriesHaving a High Specific Discharge Capacity and Processes for theSynthesis of these Materials”, and published U.S. patent application2010/0151332A (the '332 application) to Lopez et al. entitled “PositiveElectrode Materials for High Discharge Capacity Lithium Ion Batteries”,both incorporated herein by reference.

With respect to the charging of a battery with the compositelayered-layered materials, the lithium manganese oxide (Li₂MnO₃)component of the compositions can undergo a reaction to releasemolecular oxygen with an associated release of 2 Li+ ions as indicatedin equation (3):

Li₂MnO₃→MnO₂+2Li⁺+2e ⁻+½O₂.  (3)

Upon discharge, the MnO₂ composition takes up a single lithium ion and asingle electron to form LiMnO₂ so that there is an overall significantdecrease in capacity due to the irreversible reaction of the materialduring the initial charge. Evidence suggests that the reaction in Eq.(3) takes place at voltages above about 4.4 volts. Thus, with thelithium rich layer-layer material, during the first cycle charge aboveabout 4.4V, decomposition of a Li₂MnO₃ component in the high capacitymaterial can lead to oxygen loss and an irreversible capacity loss. Thematerials in principle can undergo other irreversible changes that maycoincide with the initial charge step, such as a decomposition reactionLi₂MnO₃→MnO₂+Li₂O. Such a decomposition reaction does not result in ameasured irreversible capacity loss since no electrons are generatedthat would be measured during the initial charge, but such a reaction toform inert lithium oxide could result in a loss of reversible capacityrelative to the theoretical capacity for a particular weight ofmaterial.

Carbonate and hydroxide co-precipitation processes have been performedfor the desired lithium rich metal oxide materials described herein.Generally, a solution is formed from which a metal hydroxide orcarbonate is precipitated with the desired metal stoichiometry. Themetal hydroxide or carbonate compositions from co-precipitation can besubsequently heat-treated to form the corresponding metal oxidecomposition with appropriate crystallinity. The lithium cations caneither be incorporated into the initial co-precipitation process, or thelithium can be introduced in a solid state reaction during or followingthe heat treatment to form the oxide compositions from the hydroxide orcarbonate compositions. The resulting lithium rich metal oxide materialsformed with the co-precipitation process can have improved performanceproperties.

Also, it has been found that coating the positive electrode activematerials can improve the cycling of lithium-based batteries. Thecoating can also be effective at reducing the irreversible capacity lossof the battery as well as increasing the specific capacity generally.The amount of coating material can be selected to accentuate theobserved performance improvements. The improvements of coating materialsfor lithium rich positive electrode active materials are describedfurther in the '332 application and the '853 application. Suitablecoating materials, which are generally believed to be electrochemicallyinert during battery cycling, can comprise metal fluorides, metaloxides, metal non-fluoride halides or metal phosphates. The results inthe Examples below are obtained with materials coated with metalfluorides.

For example, the general use of metal fluoride compositions as coatingsfor cathode active materials, specifically LiCoO₂ and LiMn₂O₄, isdescribed in published PCT application WO 2006/109930A to Sun et al.,entitled “Cathode Active Material Coated with Fluorine Compound forLithium Secondary Batteries and Method for Preparing the Same,”incorporated herein by reference. Improved metal fluoride coatings withappropriately engineered thicknesses are described in copending U.S.patent application Ser. No. 12/616,226 to Lopez et al, (the '226application) entitled “Coated Positive Electrode Materials for LithiumIon Batteries,” incorporated herein by reference. Suitable metal oxidecoatings are described further, for example, in copending U.S. patentapplication Ser. No. 12/870,096 to Karthikeyan et al. entitled “MetalOxide Coated Positive Electrode Materials for Lithium-Based Batteries”,incorporated herein by reference. The discovery of non-fluoride metalhalides as desirable coatings for cathode active materials is describedin copending U.S. patent application Ser. No. 12/888,131 toVenkatachalam et al., entitled “Metal Halide Coatings on Lithium IonBattery Positive Electrode Materials and Corresponding Batteries,”incorporated herein by reference.

The supplemental lithium can be introduced through one or moreapproaches. In general, a plurality of supplemental lithium sources canbe used and various types of supplemental lithium sources are described.For example, the supplemental lithium can be supplied as elementallithium metal within the initial battery structure, a sacrificiallithium source separate from the positive electrode active material,and/or lithium inserted into the negative electrode active materialprior to assembly of the battery with the positive electrode to becycled. When the source of supplemental lithium is elemental lithium ora sacrificial lithium source, the supplemental lithium is inserted intothe negative electrode active material following assembly of thebattery. If the source of supplemental lithium is within or directlyassociated with the negative electrode, the incorporation of thesupplemental lithium into the negative electrode active material can bespontaneous. If the source of supplemental lithium is not within ordirectly associated with the negative electrode, an electricalconnection between appropriate electrodes generally is used to transportelectrons to maintain electrical neutrality within the battery whilesupplemental lithium is incorporated into the negative electrode.

With respect to the inclusion of elemental lithium within the battery,the lithium metal or alloy can be associated with the negativeelectrode, the positive electrode, a distinct sacrificial electrode or acombination thereof. If the elemental lithium and the negative electrodeactive material are in contact with a common electrolyte solution andwith electrical conductivity between the material, reactions can takeplace in the battery in an open circuit configuration in which the SEIlayer forms and/or lithium is incorporated into the lithiumintercalation/alloy composition since these are spontaneous reactions.In some embodiments, the elemental lithium can be added as a powderwithin the negative electrode structure, and in additional oralternative embodiments, the elemental lithium can be placed on thesurface of the negative electrode as a foil or power with or withoutbinder.

If the elemental lithium is associated with the positive electrode or aseparate sacrificial electrode, the respective electrodes are connectedin a circuit to provide for the half reactions to occur that result inthe net transfer of lithium into the negative electrode active materialwith an appropriate flow of electrons to maintain electrical neutrality.Due to the electropositive nature of the elemental lithium, voltage mayor may not be applied across the electrode to provide for the lithiationof the negative electrode. If the elemental lithium metal is associatedwith the positive electrode, an electrical connection between thepositive electrode and the negative electrode can provide forconsumption of the elemental lithium metal in the positive electrode anddeposition of lithium in the negative electrode while providingelectrical neutrality. The insertion of lithium into the negativeelectrode from elemental lithium in the positive electrode or asacrificial electrode can be performed along with the charging step toprepare the positive electrode active material and the negativeelectrode active material for cycling.

During the process of placing supplemental lithium into the ultimatenegative electrode for the lithium ion battery, the negative electrodecan be associated in some embodiments with a sacrificial electrode,which can comprise elemental lithium or alloy thereof, and/or a positiveelectrode with a lithium sacrificial material. In these configurations,the “negative electrode” of the ultimate battery, may be in aconfiguration in which the “ultimate negative electrode” is associatedwith a cell opposite a lithium based electrode for theintercalation/alloying of lithium into the electrode. For such alithiation cell, the ultimate negative electrode may not be configuredas a negative electrode. However, the electrode can still be identifiedas the ultimate negative electrode regardless of intermediate processingof the electrode structure that can involve desired electrochemicalmanipulations.

Also, a sacrificial material can be used in the positive electrode or asacrificial electrode to supply supplemental lithium to the battery forincorporation at least partially into the negative electrode. Ingeneral, any material that provides an electrochemical lithium sourcecan act as a sacrificial source of supplemental lithium, but certainlithium sources can be desirable. It can be desirable to select asacrificial material that is not expected to cycle during normaloperation of the battery over its voltage range. For example,sacrificial compositions that are more electropositive can react duringthe charge cycle, and these materials are not likely to cycle after thefirst cycle in the positive electrode. Also, a high specific capacitysacrificial material can be useful since a reduced amount of non-cyclingweight is introduced into the cathode, and the cycling properties of thesacrificial material are not expected to be significant. Thus, suitablesacrificial materials can include, for example, lithium titanium oxide,lithiated silicon, LiCoO₂, LiFePO₄, and the like. While elementallithium metal has a very high energy density, lithium metal generallyinvolves special handling procedures due to lithium's reactivity. Thereplacement of elemental lithium, which can react violently withmoisture, with a more stable lithium source material can be desirablefrom a handling perspective. The transfer of the lithium from thesacrificial material to the negative electrode involves an electricalconnection between the positive electrode and/or a sacrificial electrodeas appropriate along with a suitable applied voltage to drive thereactions to charge the negative electrode with the lithium from thesacrificial material, based in a straightforward way on theelectro-negativity of the respective half reactions.

Alternatively or additionally, the ultimate negative electrode can beprelithiated prior to battery assembly. In general, this prelithiationof the ultimate negative electrode active material prior to batteryassembly involves an electrochemical placement of the lithium into theultimate negative electrode active material. For example, the ultimatenegative electrode can be placed in electrochemical contact with alithium source, such as a lithium foil. As shown in the examples, aseparator can be placed between the anode and the lithium foil, and anelectrical connection can be supplied to provide for the deposition oflithium into the ultimate negative electrode active material. The amountof current allowed to flow between the elemental lithium metal sourceand the ultimate negative electrode can be controlled to introduce adesired amount of lithium into the ultimate negative electrode. Apotential may or may not be applied between the elemental lithium metalsource and the ultimate negative electrode to facilitate the transfer oflithium into the ultimate negative electrode. However, other approachescan be used since the lithium is reactive and can be used to drivelithium into the ultimate negative electrode active material along withthe formation of an SEI layer. Other lithium sources can also be used toelectrochemically drive lithium into the ultimate negative electrodeactive material prior to assembly of the ultimate battery, and anappropriate voltage may be used for some of these lithium sources todrive the reaction.

As described further below, experiments suggest that the supplementallithium is gradually consumed during cycling. To retain theeffectiveness of the supplemental lithium to longer numbers of cycles,it can be desirable to load the negative electrode with a moderatelylarge amount of supplemental lithium. Thus, in general, it is desirableto load the negative electrode with supplemental lithium correspondingto at least about 3% of the capacity of the negative electrode activematerial, and up to 50% or greater of the capacity of the negativeelectrode active material can be loaded with supplemental lithium. Thetotal capacity of the negative electrode active material generally canbe at least about 3% larger than the sum of the equivalence fromsupplemental lithium and the theoretical capacity of the positiveelectrode active material.

In traditional lithium ion batteries, all of the lithium other than adissolved portion that generally remains in the electrolyte is suppliedinitially by the positive electrode active material. The battery then isinitially charged such that the lithium is transferred to the negativeelectrode active material under a charging potential. The negativeelectrode active material intercalates, alloys or otherwise incorporatesthe lithium into its structure. Upon the transfer of the lithium to thenegative electrode active material, the lithium is available tofacilitate the discharge of the battery as the lithium is transferredback to the positive electrode active material with the release ofelectrochemical energy that can be used to generate useful work.

As in conventional lithium ion batteries, for the batteries describedherein, the positive electrode active material generally is initiallyfully lithiated such that the battery is initially charged to preparethe positive electrode for subsequent discharge. It is surprisinglyfound that the inclusion of the supplemental active lithium in thenegative electrode can greatly stabilize the battery during cycling outto very large numbers of cycles. While not wanting to be limited bytheory, evidence provided herein indicates that this stability may bedue to effects at both the positive electrode and the negativeelectrode.

It has been proposed to construct a battery with a lithium-depletedpositive electrode active material, elemental lithium metal associatedwith the negative electrode and a lithium intercalation material, suchas carbon, associated with the negative electrode. This batterystructure is described further in U.S. Pat. No. 7,276,314 to Gao et al.,entitled “Lithium Metal Dispersion in Secondary Battery Anodes,”incorporated herein by reference. In these batteries, the lithium forcycling is provided by the initial lithium metal in the negativeelectrode. Similarly, the negative electrode intercalation material canbe electrochemically loaded with lithium such that the negativeelectrode provides the lithium for cycling when combined with a lithiumdepleted positive electrode. Such a structure is described in U.S. Pat.No. 5,753,388 to Kockbang et al., entitled “Process for Prelithiation ofCarbon Based Anodes for Lithium Ion Electrochemical Cells,” incorporatedherein by reference. These batteries do not provide supplemental lithiumas described herein, but these batteries only provide an alternativeapproach for the introduction of the initial lithium into the battery.

In general, the positive electrode and negative electrode capacities arerelatively balanced to avoid waste of materials, although a slightexcess of negative electrode material can be used to avoid thedeposition or plating of lithium metal during battery charging. It hasbeen proposed to incorporate lithium metal into the battery tocompensate for lithium related to SEI layer formation, which correspondswith irreversible capacity loss if the positive electrode activematerial is not lithium rich. For example, it has been proposed toincorporate an auxiliary lithium metal foil electrode in contact withthe electrolyte but separated from the electrodes to compensate forirreversible capacity loss, as described in U.S. Pat. No. 6,335,115 toMeissner, entitled “Secondary Lithium-Ion Cell With an AuxiliaryElectrode,” incorporated herein by reference. A similar structure inwhich the lithium metal foil is placed in the cell as a lithiumreservoir in electrical contact with the negative electrode is describedin U.S. Pat. No. 6,025,093 to Herr, entitled “Lithium Ion Cell,”incorporated herein by reference. Similarly, a layer of lithium has beenproposed to compensate for the large irreversible capacity lossassociated with hard carbon, as described in U.S. Pat. No. 6,737,191 toGan et al., entitled “Double Current Collector Negative Electrode Designfor Alkali Metal Ion Electrochemical Cells,” incorporated herein byreference. A partial electrochemical prelithiation of the negativeelectrode intercalation material to compensate for irreversible capacityloss has been described in U.S. Pat. No. 5,743,921 to Nazri et al.,entitled “Method of Making a Cell Using a Lithium-Deactivated CarbonAnode,” incorporated herein by reference.

A battery structure with a composite positive electrode and compositenegative electrode is described in U.S. Pat. No. 7,582,387 to Howard etal., entitled “Lithium-Ion Battery,” incorporated herein by reference.The positive electrode has two active materials in which one isinitially loaded with lithium while the other is not, and the negativeelectrode initially comprises lithium metal and an intercalationcomposition. It is asserted that this structure provides for chargingand discharging stably over a broader potential range. In addition, alayer of elemental lithium metal has been proposed to stabilize thecycling of lithium ion cell, as described in U.S. Pat. No. 5,147,739 toBeard, entitled “High Energy Electrochemical Cell Having CompositeSolid-State Anode,” incorporated herein by reference. An elementallithium coating associated with the surface of the negative electrode ornegative electrode side of the separator was also proposed for thepurpose of compensating for irreversible capacity loss as well asimproving cycling. See, U.S. Pat. No. 5,948,569 to Moses et al.,entitled “Lithium Ion Electrochemical Cell,” incorporated herein byreference. The electrochemical incorporation of lithium into negativeelectrode active material or the lithium metal have been proposed tostabilize cycling through replacement of lithium lost as a result ofirreversible capacity loss has been described in U.S. Pat. No. 5,162,176to Herr et al., entitled “Electrochemical Secondary Element,”incorporated herein by reference. The Herr '176 patent describes the useof the needle coke as the negative electrode cycling material, which hasa large irreversible capacity loss.

However, if the irreversible capacity loss is dominated by irreversiblechanges to the positive electrode active material rather than theformation of an SEI layer, there would be no purpose in adding lithiumto compensate for the irreversible capacity loss. In particular, theadded lithium cannot be incorporated into the positive electrode activematerial during discharge. So the rational of compensating forirreversible capacity loss does not make sense in the context of thelithium rich positive electrode active materials described herein.However, much more significant results have been found when supplementallithium is incorporated into batteries comprising the lithium rich metaloxides. In particular, the structure of the positive electrode activematerials is significantly stabilized for reasons that are not presentlyunderstood.

When operated at lower voltages, lithium ion batteries incorporating thelithium rich metal oxides have been stabilized to obtain moderatecycling performance, as described in copending U.S. patent applicationSer. No. 12/509,131 to Kumar et al., entitled “Lithium Ion BatteriesWith Long Cycling Performance,” incorporated herein by reference.Specifically, using a lithium rich metal oxide having an AlF₃ coating,reasonable cycling from 2.5V to 4.2V was obtained out to more than 1000cycles. However, comparable long cycling performance at higher voltageswith correspondingly higher capacities has been elusive before now.Also, further improvement in the cycling performance at lower voltagewould also be desirable.

When operated at higher voltages to access a greater part of thecapacity of the positive electrode active materials, the cyclingperformance has been observed to fade more rapidly. However, theinclusion of supplemental lithium in batteries with the lithium richpositive electrode active materials has amazingly resulted in thedramatic improvement in the cycling properties of the batteries even athigh voltage operation. This surprising improvement has been found tocorrelate with stabilization of the positive electrode active material,although increased stability of the SEI layer is also suggested by thedata. In particular, for batteries without the supplemental lithium, itis found that metals from the positive electrode active materialsmigrate to the negative electrode active materials, which indicates thatthe metals dissolute into the electrolyte indicating instability of thematerial. If the positive electrode active materials are unstable, thebattery capacity would be expected to fade since the positive electrodewould gradually not be able to take up the same quantities of lithiumduring a discharge step. It is observed that after cycling the batteriesfor a hundred cycles with supplemental lithium, non-lithium metal atomsfrom the positive electrode active materials make up no more than about5 weight percent of the negative electrode active materials, whichindicates that the positive electrode active materials are stable withrespect to cycling. The supplemental lithium in the negative electrodeprovided additional capacity in the negative electrode during cyclingeven after discharging the battery to 2 volts. Thus, after cycling for20 cycles and discharging the battery to 2 volts, the negative electrodecan be removed and further de-intercalated/de-alloyed against lithium toremove at least about 0.5 percent of the total negative electrodecapacity.

As described herein, the incorporation of supplemental lithium inbatteries with lithium rich metal oxides stabilizes the cyclingperformance of the lithium batteries. This improved performance isobtained even for cycling at high voltage such that high specificcapacities are also obtained. Using positive electrode materials thatare stabilized with a coating, the high specific capacity cyclingperformance can be maintained for hundreds of cycles with little or nocapacity fade. In particular, there is an observed synergistic effectwith high capacity lithium rich positive electrode composition alongwith the supplemental lithium that results in the extremely stablecycling properties.

It is useful to note that during charge/discharge measurements, thespecific capacity of a material depends on the rate of discharge. Thehighest specific capacity of a particular material is measured at veryslow discharge rates. In actual use, the actual specific capacity isless than the maximum value due to discharge at a faster rate. Morerealistic specific capacities can be measured using reasonable rates ofdischarge that are more similar to the rates encountered during actualuse. For example, in low to moderate rate applications, a reasonabletesting rate involves a discharge of the battery over three hours. Inconventional notation this is written as C/3 or 0.33 C. Faster or slowerdischarge rates can be used as desired, and the rates can be describedwith the same notation.

The inclusion of the added elemental lithium metal is observed toincrease the reversible capacity at a selected operating voltage so thatthe productive specific capacity increases. Thus, for the lithium richhigh capacity materials described herein, the discharge specificcapacity can be high, e.g., greater than about 240 mAh/g. This highpositive electrode specific capacity can be maintained for many cycleswith little or no fade. In some embodiments, the positive electrode hasa room temperature specific discharge capacity at the 200th cycle thatis at least about 92.5% of the 5th cycle specific discharge capacitywhen discharged from the 5th cycle to the 200th cycle at a C/3 rate. Infurther embodiments, it has been found that the cycling stability of thespecific discharge capacity is maintained at even greater dischargerates of 1 C and 2 C as well as at elevated temperatures, such as 55° C.

Rechargeable batteries have a range of uses, such as mobilecommunication devices, such as phones, mobile entertainment devices,such as MP3 players and televisions, portable computers, combinations ofthese devices that are finding wide use, as well as transportationdevices, such as automobiles and fork lifts. The batteries describedherein that incorporate improved positive electrode active materialswith respect to specific capacity, tap density, and cycling can provideimproved performance for consumers, especially for medium currentapplications. For some applications, such as hybrid vehicles, plug-inhybrid vehicles and electric vehicles, the batteries are a verysignificant cost, such that the improvements of the cycling of thebatteries can significant decrease the lifetime cost of the use of thevehicle such that the vehicles become more accessible to a broaderpublic.

Lithium Ion Battery Structure

Lithium ion batteries generally comprise a positive electrode, anegative electrode, a separator between the negative electrode and thepositive electrode and an electrolyte comprising lithium ions. Theelectrodes are generally associated with metal current collectors, suchas metal foils. Lithium ion batteries refer to batteries in which thenegative electrode active material is a material that takes up lithiumduring charging and releases lithium during discharging. Referring toFIG. 1, a battery 100 is shown schematically having a negative electrode102, a positive electrode 104 and a separator 106 between negativeelectrode 102 and positive electrode 104. A battery can comprisemultiple positive electrodes and multiple negative electrodes, such asin a stack, with appropriately placed separators. Electrolyte in contactwith the electrodes provides ionic conductivity through the separatorbetween electrodes of opposite polarity. A battery generally comprisescurrent collectors 108, 110 associated respectively with negativeelectrode 102 and positive electrode 104. The basic battery structuresand compositions are described in this section and modifications relatedto incorporation of supplemental lithium are described further below.

The nature of the negative electrode intercalation/alloying materialinfluences the resulting voltage of the battery since the voltage is thedifference between the half cell potentials at the cathode and anode.Suitable negative electrode (anode) lithium intercalation/alloyingcompositions can include, for example, graphite, synthetic graphite,coke, fullerenes, other graphitic carbons, niobium pentoxide, tinalloys, silicon, titanium oxide, tin oxide, and lithium titanium oxide,such as Li_(x)TiO₂, 0.5<x≦1 or Li_(1+x)Ti_(2−x)O₄, 0≦x≦⅓. The graphiticcarbon and metal oxide negative electrode compositions take up andrelease lithium through an intercalation or similar process. Silicon andtin alloys form alloys with the lithium metal to take up lithium andrelease lithium from the alloy to correspondingly release lithium.Additional negative electrode materials are described in published U.S.patent applications 2010/0119942 to Kumar, entitled “CompositeCompositions, Negative Electrodes with Composite Compositions andCorresponding Batteries,” and 2009/0305131 to Kumar et al., entitled“High Energy Lithium Ion Batteries with Particular Negative ElectrodeCompositions,” both of which are incorporated herein by reference.

The positive electrode active compositions and negative electrode activecompositions generally are powder compositions that are held together inthe corresponding electrode with a polymer binder. The binder providesionic conductivity to the active particles when in contact with theelectrolyte. Suitable polymer binders include, for example,polyvinylidine fluoride, polyethylene oxide, polyethylene,polypropylene, polytetrafluoroethylene, polyacrylates, rubbers, e.g.ethylene-propylene-diene monomer (EPDM) rubber or styrene butadienerubber (SBR), copolymers thereof, or mixtures thereof. The particleloading in the binder can be large, such as greater than about 80 weightpercent. To form the electrode, the powders can be blended with thepolymer in a suitable liquid, such as a solvent for the polymer. Theresulting paste can be pressed into the electrode structure.

The positive electrode composition, and possibly the negative electrodecomposition, generally also comprises an electrically conductive powderdistinct from the electroactive composition. Suitable supplementalelectrically conductive powders include, for example, graphite, carbonblack, metal powders, such as silver powders, metal fibers, such asstainless steel fibers, and the like, and combinations thereof.Generally, a positive electrode can comprise from about 1 weight percentto about 25 weight percent, and in further embodiments from about 2weight percent to about 15 weight percent distinct electricallyconductive powder. A person of ordinary skill in the art will recognizethat additional ranges of amounts of electrically conductive powders andpolymer binders within the explicit ranges above are contemplated andare within the present disclosure.

The electrode generally is associated with an electrically conductivecurrent collector to facilitate the flow of electrons between theelectrode and an exterior circuit. The current collector can comprisemetal, such as a metal foil or a metal grid. In some embodiments, thecurrent collector can be formed from nickel, aluminum, stainless steel,copper or the like. The electrode material can be cast as a thin filmonto the current collector. The electrode material with the currentcollector can then be dried, for example in an oven, to remove solventfrom the electrode. In some embodiments, the dried electrode material incontact with the current collector foil or other structure can besubjected to a pressure, such as, from about 2 to about 10 kg/cm²(kilograms per square centimeter).

The separator is located between the positive electrode and the negativeelectrode. The separator is electrically insulating while providing forat least selected ion conduction between the two electrodes. A varietyof materials can be used as separators. Commercial separator materialsare generally formed from polymers, such as polyethylene and/orpolypropylene that are porous sheets that provide for ionic conduction.Commercial polymer separators include, for example, the Celgard® line ofseparator material from Hoechst Celanese, Charlotte, N.C. Also,ceramic-polymer composite materials have been developed for separatorapplications. These composite separators can be stable at highertemperatures, and the composite materials can significantly reduce thefire risk. The polymer-ceramic composites for separator materials aredescribed further in U.S. patent application 2005/0031942A to Hennige etal., entitled “Electric Separator, Method for Producing the Same and theUse Thereof,” incorporated herein by reference. Polymer-ceramiccomposites for lithium ion battery separators are sold under thetrademark Separion® by Evonik Industries, Germany.

We refer to solutions comprising solvated ions as electrolytes, andionic compositions that dissolve to form solvated ions in appropriateliquids are referred to as electrolyte salts. Electrolytes for lithiumion batteries can comprise one or more selected lithium salts.Appropriate lithium salts generally have inert anions. Suitable lithiumsalts include, for example, lithium hexafluorophosphate, lithiumhexafluoroarsenate, lithium bis(trifluoromethyl sulfonyl imide), lithiumtrifluoromethane sulfonate, lithium tris(trifluoromethylsulfonyl)methide, lithium tetrafluoroborate, lithium perchlorate,lithium tetrachloroaluminate, lithium chloride, lithium difluoro oxalatoborate, and combinations thereof. Traditionally, the electrolytecomprises a 1 M concentration of the lithium salts, although greater orlesser concentrations can be used.

For lithium ion batteries of interest, a non-aqueous liquid is generallyused to dissolve the lithium salt(s). The solvent generally does notdissolve the electroactive materials. Appropriate solvents include, forexample, propylene carbonate, dimethyl carbonate, diethyl carbonate,2-methyl tetrahydrofuran, dioxolane, tetrahydrofuran, methyl ethylcarbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, formamide,dimethyl formamide, triglyme (tri(ethylene glycol) dimethyl ether),diglyme (diethylene glycol dimethyl ether), DME (glyme or1,2-dimethyloxyethane or ethylene glycol dimethyl ether), nitromethaneand mixtures thereof. Particularly useful solvents for high voltagelithium-ion batteries are described further in copending U.S. patentapplication Ser. No. 12/630,992 filed on Dec. 4, 2009 to Amiruddin etal. (the '992 application), entitled “Lithium Ion Battery With HighVoltage Electrolytes and Additives,” incorporated herein by reference.

The electrodes described herein can be incorporated into variouscommercial battery designs. For example, the cathode compositions can beused for prismatic shaped batteries, wound cylindrical batteries, coinbatteries or other reasonable battery shapes. The batteries can comprisea single cathode structure or a plurality of cathode structuresassembled in parallel and/or series electrical connection(s).

In some embodiments, the positive electrode and negative electrode canbe stacked with the separator between them, and the resulting stackedstructure can be placed into a cylindrical or prismatic configuration toform the battery structure. Appropriate electrically conductive tabs canbe welded or the like to the current collectors, and the resultingjellyroll or stack structure can be placed into a metal canister orpolymer package, with the negative tab and positive tab welded toappropriate external contacts. Electrolyte is added to the canister, andthe canister is sealed to complete the battery. Some presently usedrechargeable commercial batteries include, for example, the cylindrical18650 batteries (18 mm in diameter and 65 mm long) and 26700 batteries(26 mm in diameter and 70 mm long), although other battery sizes can beused. Pouch batteries can be constructed as described in published U.S.patent application 2009/0263707 to Buckley et al, entitled “High EnergyLithium Ion Secondary Batteries”, incorporated herein by reference.

Positive Electrode Active Compositions

In some embodiments, the lithium ion battery positive electrodematerials can be any reasonable positive electrode active material, suchas stoichiometric layered cathode materials with hexagonal latticestructures, such as LiCoO₂, LiNiO₂, LiMnO₂, or the like; cubic spinelcathode materials such as LiMn₂O₄, Li₄Mn₅O₁₂, or the like; olivineLiMPO₄ (M=Fe, Co, Mn, combinations thereof and the like) type materials;layered cathode materials such as Li_(1+x)(NiCoMn)_(0.33−x)O₂ (0≦x<0.3)systems; layer-layer composites, such as xLi₂MnO₃.(1−x)LiMO₂ where M canbe Ni, Co, Mn, combinations thereof and the like; and compositestructures like layered-spinel structures such as LiMn₂O₄.LiMO₂. Inadditional or alternative embodiments, a lithium rich composition can bereferenced relative to a composition LiMO₂, where M is one or moremetals with an average oxidation state of +3. Generally, the lithiumrich compositions can be represented approximately with a formulaLi_(1+x)M_(1−y)O₂, where M represents one or more non-lithium metals andy is related to x based on the average valance of the metals. In someembodiments, x is from about 0.01 to about 0.33, and y is from aboutx−0.2 to about x+0.2 with the proviso that y≧0. In the layered-layeredcomposite compositions, x is approximately equal to y. In general, theadditional lithium in the lithium rich compositions is accessed athigher voltages such that the initial charge takes place at a relativelyhigher voltage to access the additional capacity.

Lithium rich positive electrode active materials of particular interestcan be represented approximately by a formulaLi_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O_(2−z)F_(z), where b ranges from about0.01 to about 0.3, α ranges from about 0 to about 0.4, β range fromabout 0.2 to about 0.65, γ ranges from 0 to about 0.46, δ ranges from 0to about 0.15 and z ranges from 0 to about 0.2 with the proviso thatboth α and γ are not zero, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B,Zr, Ti, Ca, Ce, Y, Nb, Cr, Fe, V, Li or combinations thereof. A personof ordinary skill in the art will recognize that additional ranges ofparameter values within the explicit compositional ranges abovecontemplated and are within the present disclosure. To simplify thefollowing discussion in this section, the optional fluorine dopant isnot discussed further. Desirable lithium rich compositions with afluorine dopant are described further in copending U.S. patentapplication Ser. No. 12/569,606 to Kumar et al., entitled “FluorineDoped Lithium Rich Metal Oxide Positive Electrode Battery Materials WithHigh Specific Capacity and Corresponding Batteries,” incorporated hereinby reference. Compositions in which A is lithium as a dopant forsubstitution for Mn are described in copending U.S. patent applicationSer. No. 12/870,295 to Venkatachalam et al., entitled Lithium DopedCathode Material,” incorporated herein by reference. The specificperformance properties obtained with +2 metal cation dopants, such asMg⁺², are described in copending U.S. patent application Ser. No.12/753,312 to Karthikeyan et al., entitled “Doped Positive ElectrodeActive Materials and Lithium Ion Secondary Batteries ConstructedTherefrom,” incorporated herein by reference.

If b+α+β+γ+δ is approximately equal to 1, the positive electrodematerial with the formula above can be represented approximately in twocomponent notation as x Li₂M′O₃.(1−x)LiMO₂ where 0<x<1, M is one or moremetal cations with an average valance of +3 within some embodiments atleast one cation being a Mn ion or a Ni ion and where M′ is one or moremetal cations, such as Mn⁺⁴, with an average valance of +4. It isbelieved that the layered-layered composite crystal structure has astructure with the excess lithium supporting the stability of thematerial. For example, in some embodiments of lithium rich materials, aLi₂MnO₃ material may be structurally integrated with a layered LiMO₂component where M represents selected non-lithium metal elements orcombinations thereof. These compositions are described generally, forexample, in U.S. Pat. No. 6,680,143 to Thackeray et al., entitled“Lithium Metal Oxide Electrodes for Lithium Cells and Batteries,”incorporated herein by reference.

Recently, it has been found that the performance properties of thepositive electrode active materials can be engineered around thespecific design of the composition stoichiometry. The positive electrodeactive materials of particular interest can be represented approximatelyin two component notation as x Li₂MnO₃.(1−x) LiMO₂, where M is one ormore metal elements with an average valance of +3 and with one of themetal elements being Mn and with another metal element being Ni and/orCo. In general, 0<x<1, but in some embodiments 0.03≦x≦0.55, in furtherembodiments 0.075≦x≦0.50, in additional embodiments 0.1≦x≦0.45, and inother embodiments 0.15≦x≦0.425. A person of ordinary skill in the artwill recognize that additional ranges within the explicit ranges ofparameter x above are contemplated and are within the presentdisclosure. For example, M can be a combination of nickel, cobalt andmanganese, which, for example, can be in oxidation states Ni⁺², Co⁺³,and Mn⁺⁴ within the initial lithium manganese oxides. The overallformula for these compositions can be written asLi_(2(1+x)/(2+x))Mn_(2x/(2+x))M_((2−2x)/(2x+x))O₂. In the overallformula, the total amount of manganese has contributions from bothconstituents listed in the two component notation. Thus, in some sensethe compositions are manganese rich.

In some embodiments, M can be written as Ni_(u)Mn_(v)Co_(w)A_(y). Forembodiments in which y=0, this simplifies to Ni_(u)Mn_(v)Co_(w). If Mincludes Ni, Co, Mn, and optionally A the composition can be writtenalternatively in two component notation and single component notation asthe following.

xLi₂MnO₃.(1−x)LiNi_(u)Mn_(v)Co_(w)A_(y)O₂,  (1)

Li_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O₂,  (2)

with u+v+w+y≈1 and b+α+β+γ+δ≈1. The reconciliation of these two formulasleads to the following relationships:

b=x/(2+x),

α=2u(1−x)/(2+x),

β=2x/(2+x)+2v(1−x)/(2+x),

γ=2w(1−x)/(2+x),

δ=2y(1−x)/(2+x),

and similarly,

x=2b/(1−b),

u=α/(1−3b),

v=(β−2 b)/(1−3b),

w=γ/(1−3b),

y=δ/(1−3b).

In some embodiments, it may be desirable to have u≈v, such that LiNi_(u)Mn_(v)Co_(w)A_(y)O₂ becomes approximately LiNi_(u)Mn_(v)Co_(w)A_(y)O₂. In this composition, when y=0, the averagevalance of Ni, Co and Mn is +3, and if u≈v, then these elements can havevalances of approximately Ni⁺², Co⁺³ and Mn⁺⁴ to achieve the averagevalance. When the lithium is hypothetically fully extracted, all of theelements go to a +4 valance. A balance of Ni and Mn can provide for Mnto remain in a +4 valance as the material is cycled in the battery. Thisbalance avoids the formation of Mn⁺³, which has been associated withdissolution of Mn into the electrolyte and a corresponding loss ofcapacity.

In further embodiments, the composition can be varied around the formulaabove such that Li Ni_(u+Δ)Mn_(u−Δ)Co_(w)A_(y)O₂, where the absolutevalue of Δ generally is no more than about 0.3 (i.e., −0.3≦Δ≦0.3), inadditional embodiments no more than about 0.2 (−0.2≦Δ≦0.2) in someembodiments no more than about 0.175 (−0.175≦Δ≦0.175) and in furtherembodiments no more than about 0.15 (−0.15≦Δ≦0.15). Desirable ranges forx are given above. With 2u+w+y≈1, desirable ranges of parameters are insome embodiments 0≦w≦1, 0≦u≦0.5, 0≦y≦0.1 (with the proviso that both u+Δand w are not zero), in further embodiments, 0.1≦w≦0.6, 0.1≦u≦0.45,0≦y≦0.075, and in additional embodiments 0.2≦w≦0.5, 0.2≦u≦0.4, 0≦y≦0.05.A person of ordinary skill in the art will recognize that additionalranges of composition parameters within the explicit ranges above arecontemplated and are within the present disclosure. As used herein, thenotation (value1≦variable≦value2) implicitly assumes that value 1 andvalue 2 are approximate quantities. The engineering of the compositionto obtain desired battery performance properties is described further inthe '976 application cited above.

A co-precipitation process has been performed for the desired lithiumrich metal oxide materials described herein having nickel, cobalt,manganese and additional optional metal cations in the composition andexhibiting the high specific capacity performance. In addition to thehigh specific capacity, the materials can exhibit a good tap densitywhich leads to high overall capacity of the material in fixed volumeapplications. Specifically, lithium rich metal oxide compositions formedby the co-precipitation process were used in coated forms to generatethe results in the Examples below.

Specifically, the synthesis methods based on co-precipitation have beenadapted for the synthesis of compositions with the formulaLi_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O_(2−z)F_(z), as described above. In theco-precipitation process, metal salts are dissolved into an aqueoussolvent, such as purified water, with a desired molar ratio. Suitablemetal salts include, for example, metal acetates, metal sulfates, metalnitrates, and combination thereof. The concentration of the solution isgenerally selected between 1M and 3M. The relative molar quantities ofmetal salts can be selected based on the desired formula for the productmaterials. Similarly, the dopant elements can be introduced along withthe other metal salts at the appropriate molar quantity such that thedopant is incorporated into the precipitated material. The pH of thesolution can then be adjusted, such as with the addition of Na₂CO₃and/or ammonium hydroxide, to precipitate a metal hydroxide or carbonatewith the desired amounts of metal elements. Generally, the pH can beadjusted to a value between about 6.0 to about 12.0. The solution can beheated and stirred to facilitate the precipitation of the hydroxide orcarbonate. The precipitated metal hydroxide or carbonate can then beseparated from the solution, washed and dried to form a powder prior tofurther processing. For example, drying can be performed in an oven atabout 110° C. for about 4 to about 12 hours. A person of ordinary skillin the art will recognize that additional ranges of process parameterswithin the explicit ranges above are contemplated and are within thepresent disclosure.

The collected metal hydroxide or carbonate powder can then be subjectedto a heat treatment to convert the hydroxide or carbonate composition tothe corresponding oxide composition with the elimination of water orcarbon dioxide. Generally, the heat treatment can be performed in anoven, furnace or the like. The heat treatment can be performed in aninert atmosphere or an atmosphere with oxygen present. In someembodiments, the material can be heated to a temperature of at leastabout 350° C. and in some embodiments from about 400° C. to about 800°C. to convert the hydroxide or carbonate to an oxide. The heat treatmentgenerally can be performed for at least about 15 minutes, in furtherembodiments from about 30 minutes to 24 hours or longer, and inadditional embodiments from about 45 minutes to about 15 hours. Afurther heat treatment can be performed at a second higher temperatureto improve the crystallinity of the product material. This calcinationstep for forming the crystalline product generally is performed attemperatures of at least about 650° C., and in some embodiments fromabout 700° C. to about 1200° C., and in further embodiments from about700° C. to about 1100° C. The calcination step to improve the structuralproperties of the powder generally can be performed for at least about15 minutes, in further embodiments from about 20 minutes to about 30hours or longer, and in other embodiments from about 1 hour to about 36hours. The heating steps can be combined, if desired, with appropriateramping of the temperature to yield desired materials. A person ofordinary skill in the art will recognize that additional ranges oftemperatures and times within the explicit ranges above are contemplatedand are within the present disclosure.

The lithium element can be incorporated into the material at one or moreselected steps in the process. For example, a lithium salt can beincorporated into the solution prior to or upon performing theprecipitation step through the addition of a hydrated lithium salt. Inthis approach, the lithium species is incorporated into the hydroxide orcarbonate material in the same way as the other metals. Also, due to theproperties of lithium, the lithium element can be incorporated into thematerial in a solid state reaction without adversely affecting theresulting properties of the product composition. Thus, for example, anappropriate amount of lithium source generally as a powder, such asLiOH.H₂O, LiOH, Li₂CO₃, or a combination thereof, can be mixed with theprecipitated metal carbonate or metal hydroxide. The powder mixture isthen advanced through the heating step(s) to form the oxide and then thecrystalline final product material.

Further details of the hydroxide co-precipitation process are describedin the '853 application referenced above. Further details of thecarbonate co-precipitation process are described in the '332 applicationreferenced above.

Coatings and Formation of Coatings

Inorganic coatings, such as metal halide coatings and metal oxidecoatings, have been found to significantly improve the performance oflithium ion batteries, although the coatings are believed to be inertwith respect to battery cycling. In particular, the cycling propertiesof the batteries formed from coated lithium metal oxide have been foundto significantly improve from the uncoated material. Additionally, thespecific capacity of the batteries also shows desirable properties withthe coatings, and the irreversible capacity loss of the first cycle ofthe battery can be reduced in some embodiments. In the Examples below,performance properties are obtained for the active materials coated withmagnesium fluoride, MgF₂, and with aluminum fluoride, AlF₃.

With respect to metal oxide and metal halide coatings, a coating with acombination of metal and/or metalloid elements can be used for thecoating compositions. Suitable metals and metalloid elements for thefluoride coatings include, for example, Al, Bi, Ga, Ge, In, Mg, Pb, Si,Sn, Ti, Tl, Zn, Zr and combinations thereof. Aluminum fluoride can be adesirable coating material since it has a reasonable cost and isconsidered environmentally benign. The metal fluoride coating aredescribed generally in published PCT application WO 2006/109930A to Sunet al., entitled “Cathode Active Materials Coated with Fluorine Compoundfor Lithium Secondary Batteries and Method for Preparing the Same,”incorporated herein by reference. It has been found that metal/metalloidfluoride coatings can significantly improve the performance of lithiumrich layered compositions for lithium ion secondary batteries. See, forexample, the '853 application and the '332 application cited above, aswell as the '226 application. Desirable performance results fornon-fluoride metal halide coatings have been described in copending U.S.patent application Ser. No. 12/888,131 to Venkatachalum et al., entitled“Metal Halide Coatings on Lithium Ion Battery Positive ElectrodeMaterials and Corresponding Batteries,” incorporated herein byreference.

An increase in capacity and a reduction in irreversible capacity losswere noted with Al₂O₃ coatings by Wu et al., “High Capacity,Surface-Modified Layered Li[Li_((1−x)/3)Mn_((2−x)/3)Ni_(x/3)Co_(x/3)]O₂Cathodes with Low Irreversible Capacity Loss,” Electrochemical and SolidState Letters, 9 (5) A221-A224 (2006), incorporated herein by reference.The use of a LiNiPO₄ coating to obtain improved cycling performance isdescribed in an article to Kang et al. “Enhancing the rate capability ofhigh capacity xLi₂MnO₃ (1−x)LiMO₂ (M=Mn, Ni, Co) electrodes by Li—Ni—PO₄treatment,” Electrochemistry Communications 11, 748-751 (2009),incorporated herein by reference, and this article can be referencedgenerally with respect to the formation of metal phosphate coatings.Desirable properties of metal oxide coatings on lithium rich positiveelectrode active materials are described further in copending U.S.patent application Ser. No. 12/870,096 to Karthikeyan et al., entitled“Metal Oxide Coated Positive electrode Materials for Lithium-BasedBatteries,” incorporated herein by reference.

In some embodiments, the coating improves the specific capacity of thebatteries even though the coating itself is not electrochemicallyactive. However, the coatings also influence other properties of theactive material, such as the average voltage, thermal stability andimpedance. The selection of the coating properties can incorporateadditional factors related to the overall range of properties of thematerial.

In general, the coatings can have an average thickness of no more than25 nm, in some embodiments from about 0.5 nm to about 20 nm, in otherembodiments from about 1 nm to about 12 mm, in further embodiments from1.25 nm to about 10 nm and in additional embodiments from about 1.5 nmto about 8 nm. A person of ordinary skill in the art will recognize thatadditional ranges of coating material within the explicit ranges aboveare contemplated and are within the present disclosure. The amount ofcoating materials to achieve desired improvement in battery performancecan be related to the particle size and surface area of the uncoatedmaterial. Further discussion of the effects of coating thickness on theperformance properties for coated lithium rich lithium metal oxides isfound in the '226 application cited above.

A metal fluoride coating can be deposited using a solution basedprecipitation approach. A powder of the positive electrode material canbe mixed in a suitable solvent, such as an aqueous solvent. A solublecomposition of the desired metal/metalloid can be dissolved in thesolvent. Then, NH₄F can be gradually added to the dispersion/solution toprecipitate the metal fluoride. The total amount of coating reactantscan be selected to form the desired thickness of coating, and the ratioof coating reactants can be based on the stoichiometry of the coatingmaterial. The coating mixture can be heated during the coating processto reasonable temperatures, such as in the range from about 60° C. toabout 100° C. for aqueous solutions from about 20 minutes to about 48hours, to facilitate the coating process. After removing the coatedelectroactive material from the solution, the material can be dried andheated to temperatures generally from about 250° C. to about 600° C. forabout 20 minutes to about 48 hours to complete the formation of thecoated material. The heating can be performed under a nitrogenatmosphere or other substantially oxygen free atmosphere.

An oxide coating is generally formed through the deposition of aprecursor coating onto the powder of active material. The precursorcoating is then heated to form the metal oxide coating. Suitableprecursor coating can comprise corresponding metal hydroxides, metalcarbonates or metal nitrates. The metal hydroxides and metal carbonateprecursor coating can be deposited through a precipitation process sincethe addition of ammonium hydroxide and/or ammonium carbonate can be usedto precipitate the corresponding precursor coatings. A metal nitrateprecursor coating can be deposited through the mixing of the activecathode powder with a metal nitrate solution and then evaporating thesolution to dryness to form the metal nitrate precursor coating. Thepowder with a precursor coating can be heated to decompose the coatingfor the formation of the corresponding metal oxide coating. For example,a metal hydroxide or metal carbonate precursor coating can be heated toa temperature from about 300° C. to about 800° C. for generally fromabout 1 hr to about 20 hrs. Also, a metal nitrate precursor coatinggenerally can be heated to decompose the coating at a temperature fromabout 250° C. to about 550° C. for at least about 30 minutes. A personof ordinary skill in the art can adjust these processing conditionsbased on the disclosure herein for a specific precursor coatingcomposition.

Ultimate Negative Electrode and Supplemental Lithium

The general formation of an ultimate negative electrode for a lithiumion battery is described above. Also as noted above, various approachescan be used for the introduction of supplemental lithium into thebattery, although following corresponding initial reactions and/orcharging, the ultimate negative electrode becomes charged with excesslithium for cycling from the supplemental lithium. With respect to theultimate negative electrode in batteries having supplemental lithium,the structure and/or composition of the ultimate negative electrode canchange relative to its initial structure and composition following thefirst cycle as well as following additional cycling. Depending on theapproach for the introduction of the supplemental lithium, the positiveelectrode may initially include a source of supplemental lithium and/ora sacrificial electrode can be introduced comprising supplementallithium.

With respect to initial structure of the ultimate negative electrode, insome embodiments, the negative electrode has no changes due to thesupplemental lithium. In particular, if the supplemental lithium isinitially located in the positive electrode or a separate electrode, thenegative electrode can be an unaltered form with no lithium presentuntil the battery is charged or at least until the circuit is closedbetween the ultimate negative electrode and the electrode with thesupplemental lithium in the presence of electrolyte and a separator. Forexample, the positive electrode or supplemental electrode can compriseelemental lithium, lithium alloy and/or other sacrificial lithiumsource.

A schematic diagram of a cell with a lithium source external to theultimate negative electrode is shown in FIG. 2. Cell 112 comprisesultimate negative electrode 114, positive electrode 116, first separator118 between ultimate negative electrode 114 and positive electrode 116,optional sacrificial electrode 120 and optional second separator 122between ultimate negative electrode 114 and sacrificial electrode 120.Cell 112 further comprises current collectors 124, 126, 128 associatedrespectively with ultimate negative electrode 114, positive electrode116 and sacrificial electrode 120. In some embodiments, positiveelectrode 116 comprises a supplemental lithium source 130 in addition tothe positive electrode active material 132. External circuit 134connects ultimate negative electrode 114 and positive electrode 116, andexternal circuit 136 connects ultimate negative electrode 114 andsacrificial electrode 120. Sacrificial electrode 120 can compriselithium foil and/or other supplemental lithium source, which may besupported with a polymer binder.

A cell, such as shown schematically in FIG. 2, can be contacted with anappropriate electrolyte in an appropriate vessel, such as a batteryhousing, beaker or other suitable vessel in an assembly to hold theelectrodes together if not held together with a housing. If asacrificial electrode is present, external circuit 136 can be closed tointercalate/alloy lithium into the ultimate negative electrode from thesacrificial electrode. In general, the sacrificial electrode can have aselected fraction of the capacity of the ultimate negative electrodesuch that a desired amount of supplemental lithium can be deposited intothe negative electrode. A portion of the lithium from the sacrificialelectrode can be consumed in formation of an SEI layer, which can bepartially or fully formed during the charge from the sacrificialelectrode. The current can be flowed between the sacrificial electrodeand the ultimate negative electrode at a constant current, constantvoltage or other desired rate. After the priming of the ultimatenegative electrode using the sacrificial electrode is complete, externalcircuit 136 generally is disconnected and not used further.

If sacrificial lithium is included in the positive electrode, thelithium from the sacrificial lithium source is loaded into the negativeelectrode during the charge reaction. The voltage during the chargingbased on the sacrificial lithium source may be significantly differentthan the voltage when the charging is performed based on the positiveelectrode active material. For example, elemental lithium in thepositive electrode can charge the negative electrode active materialwithout application of an external voltage since oxidation of theelemental lithium drives the reaction. For some sacrificial lithiumsource materials, an external voltage is applied to oxidize thesacrificial lithium source in the positive electrode and drive lithiuminto the negative electrode active material. The charging generally canbe performed using a constant current, a stepwise constant voltagecharge or other convenient charging scheme. However, at the end of thecharging process, the battery should be charged to a desired voltage,such as 4.5V.

In further embodiments, at least a portion of the supplemental lithiumis initially associated with the negative electrode. For example, thesupplemental lithium can be in the form of elemental lithium, a lithiumalloy or other lithium source that is more electronegative than thenegative electrode active material. After the negative electrode is incontact with electrolyte, a reaction can take place, and thesupplemental lithium is transferred to the negative electrode activematerial. During this process, the SEI layer is also formed. Thus, thesupplemental lithium is loaded into the negative electrode activematerial with at least a portion consumed in formation of the SEI layer.The excess lithium released from the lithium rich positive electrodeactive material is also deposited into the negative electrode activematerial during eventual charging of the battery. The supplementallithium placed into the negative electrode should be moreelectronegative than the active material in the negative electrode sincethere is no way of reacting the supplemental lithium source with theactive material in the same electrode through the application of avoltage.

Supplemental lithium associated with the negative electrode can beincorporated as a powder within the negative electrode, and such astructure is shown schematically in FIG. 3. Referring to FIG. 3,negative electrode 140 is associated with current collector 142.Negative electrode 140 comprises active negative electrode composition144 and supplemental lithium source 146 within a polymer binder matrix148, and any electrically conductive powder if present is not shown. Inadditional or alternative embodiments, the supplemental lithium isplaced along the surface of the electrode, as shown in FIGS. 4A and 4B.Referring to FIG. 4A, negative electrode 150 is placed on currentcollector 152. Negative electrode 150 comprises an active layer 154 withan active negative electrode composition 156 and supplemental lithiumsource layer 158 on the surface of active layer 154. Supplementallithium source layer 158 can comprise a foil sheet of lithium or lithiumalloy, supplemental lithium powder within a polymer binder and/orparticles of supplemental lithium source material embedded on thesurface of active layer 154. An alternative configuration is shown inFIG. 4B in which supplemental lithium source layer 160 is between activelayer 162 and current collector 164. Also, in some embodiments, thenegative electrode can comprise supplemental lithium source layers onboth surfaces of the active layer, which is essentially a combination ofthe embodiments in FIGS. 4A and 4B.

In additional embodiments, at least a portion of the supplementallithium can be supplied to the ultimate negative electrode activematerial prior to assembly of the battery. An electrode with partiallypreloaded lithium is shown schematically in FIG. 5. As shown in FIG. 5,ultimate negative electrode 170 is in contact with current collector172. Ultimate negative electrode 170 comprises partially loaded activematerial 174, in which the partially loaded active material has aselected degree of loading of lithium through intercalation/alloying orthe like.

For example, for the preloading of the ultimate negative electrodeactive material, the ultimate negative electrode active material can becontacted with electrolyte and a lithium source, such as elementallithium, lithium alloy or other sacrificial lithium source that is moreelectronegative than the ultimate negative electrode active material. Anexperimental arrangement to perform such a preloading of lithium isshown schematically in FIG. 6. Electrode 180 with active material 182formed on current collector 184 is placed in vessel 186 containingelectrolyte 188 and a sheet of lithium source material 190 contactingelectrode 180. The sheet of lithium source material can comprise lithiumfoil, lithium alloy foil or a lithium source material in a polymerbinder optionally along with an electrically conductive powder, which isin direct contact with the ultimate negative electrode to be preloadedwith lithium such that electrons can flow between the materials tomaintain electrical neutrality while the respective reactions takeplace, and ultimate negative electrode 180 should also have contact withelectrolyte 188 to provide for ion transfer. In the ensuing reaction,lithium is loaded into the ultimate negative electrode active materialthrough intercalation, alloying or the like. In alternative oradditional embodiments, the ultimate negative electrode active materialcan be mixed in the electrolyte and the lithium source material forincorporation of the supplemental lithium prior to formation into anelectrode with a polymer binder so that the respective materials canreact in the electrolyte spontaneously.

In some embodiments, the lithium source within an electrode can beassembled into a cell with the ultimate negative electrode to bepreloaded with lithium. A separator can be placed between the respectiveelectrodes. Current can be allowed to flow between the electrodes.Depending on the composition of the lithium source it may or may not benecessary to apply a voltage to drive the lithium deposition within theultimate negative electrode active material, although it may bedesirable to apply a voltage nevertheless to control the rate ofreaction. An apparatus to perform this lithiation process is shownschematically in FIG. 7. Referring to FIG. 7, container 200 holdselectrolyte 202 and cell 204. Cell 204 comprises ultimate negativeelectrode 206, current collector 208, separator 210 and sacrificialelectrode 212 that comprises the lithium source. A convenientsacrificial electrode comprises lithium foil, lithium powder embedded ina polymer or lithium alloys, although any electrode with extractablelithium can be used.

The container for the lithiation cell can comprise a conventionalbattery housing, a beaker, or any other convenient structure. While aconventional battery housing can provide a low internal impedance due toappropriate designs, the housing is eventually opened to remove thenegative electrode for assembly of the final battery structure. Theseparator is not needed as long as the electrodes are electricallyisolated, but the close proximity of the electrodes can reduce internalimpedance. This configuration provides the advantage of being able tomeasure the current flow to meter the degree of lithiation of theultimate negative electrode. Furthermore, the ultimate negativeelectrode can be cycled once or more than once in which the ultimatenegative electrode active material is loaded close to full loading withlithium. In this way, the SEI layer can be formed with a desired degreeof control during the preloading with lithium of the ultimate negativeelectrode active material. In this way, the ultimate negative electrodeis fully formed during the preparation of the ultimate negativeelectrode with a selected preloading with lithium.

In summary, the initial negative electrode assembled into the batteryfor cycling can have a structure with no supplemental lithium associatedwith the electrode, a structure with supplemental lithium that is notassociated with the active material for cycling or a structure in whichat least a portion of the supplemental lithium is inserted into thenegative electrode active material and the SEI layer is partially orfully formed. If the negative electrode initially is associated withsupplemental lithium that is not associated with the active material forcycling, the reaction to insert the supplemental lithium into the activematerial and for SEI formation generally can begin once the battery isinfused with electrolyte. In any case, by the completion of the firstcharge cycle, the supplemental lithium is generally associated with thenegative electrode active material, and the SEI layer is generallyformed.

In general, the lithium source can comprise, for example, elementallithium, a lithium alloy or a lithium composition, such as a lithiummetal oxide, that can release lithium from the composition. Elementallithium can be in the form of a foil and/or a powder. Elemental lithium,especially in powder form, can be coated to stabilize the lithium forhandling purposes, and commercial lithium powders, such as powders fromFMC Corporation, are sold with proprietary coatings for stability. Thecoatings generally do not alter the performance of the lithium powdersfor electrochemical applications. Lithium alloys include, for example,lithium silicon alloys and the like. Lithium composition withintercalated lithium can be used in some embodiments, and suitablecompositions include, for example, lithium titanium oxide, lithium tinoxide, and the like.

In general, the amount of supplemental lithium preloaded or available toload into the negative electrode active composition can be in an amountof at least about 2.5% of capacity, in further embodiments from about 3percent to about 90 percent of capacity and in additional embodimentsfrom about 5 percent to about 80 percent of the negative electrodeactive material capacity. Another parameter of interest related to thetotal balance of the negative electrode active material against thetotal available active lithium, which is the sum of the supplementallithium and the positive electrode theoretical capacity. In someembodiments, the total available active lithium can be no more thanabout 110 percent of the negative electrode capacity, in furtherembodiments, no more than 105 percent and in further embodiments, fromabout 65 percent to about 100 percent and in further embodiments fromabout 70 to about 97.5 percent of the negative electrode activecapacity. In some traditional batteries, the negative electrode isbalanced at 107% of positive electrode capacity, which corresponds with93.5% active lithium relative to the negative electrode capacity. Whilevalues of active lithium greater than 100% of the negative electrodecapacity can result in plating of lithium in the negative electrode,evidence herein indicates that lithium is consumed with cycling so amodest amount of initial lithium that may plate in the negativeelectrode may be consumed prior to dendrite formation. A person ofordinary skill in the art will recognize that additional ranges oflithium preloading within the explicit ranges above are contemplated andare within the present disclosure.

The supplemental lithium can be detected in the negative electrode aftercycling the battery. After discharging the battery, the positiveelectrode active material is essentially loaded with the lithium thatcan be accepted back into the positive electrode active material overthe operating voltage range of the cell. In some embodiments, thebattery can be discharged to 2V, or as an alternative expression, to astate discharged 98% of the discharge capacity. If no supplementallithium is included in the battery, after formation and cycling, someexcess lithium remains in the negative electrode presumably due to theirreversible changes to the lithium rich active compositions in thepositive electrode in excess of lithium that is consumed for SEI layerformation. If supplemental lithium is included, significantly greateramounts of excess lithium can be detected in the negative electrodeafter discharge. The amount of excess lithium has been found to diminishwith further cycling. The excess lithium can be determined by removingthe negative electrode and de-intercalating/de-alloying the negativeelectrode against lithium metal. After 20 cycles over the selectedvoltage range of the battery, such as between 4.5 V and 2V, the batterycan be discharged, and the negative electrode harvested to measure itsresidual capacity. In particular, the battery can be discharged to 98%of the discharge capacity prior to disassembly. After retrieval of thenegative electrode, the negative electrode can have a residual capacityof at least about 0.5% of the total capacity, in further embodiments atleast about 1% and in additional embodiments at least about 2%. It isnot necessary to harvest the entire negative electrode since the percentcapacity can be evaluated for a portion of the electrode. Afterde-intercalation/de-alloying, the electrode can be fully loaded withlithium up to an appropriate voltage to measure the full capacity toobtain the percentage residual capacity. After 500 cycles between 4.5Vand 2V, the negative electrode can have a capacity of 0.2%, in furtherembodiments at least about 0.25% and in additional embodiments at leastabout 0.5%. A person of ordinary skill in the art will recognize thatadditional ranges of discharged negative electrode residual capacitieswithin the explicit ranges above are contemplated and are within thepresent disclosure.

The presence of the supplemental lithium during cycling is observed tostabilize the cycling of the battery and in particular for the stabilityof the positive electrode. In particular, it has been found that thetransition metals leach from the lithium rich positive electrodematerial into the electrolyte. The transition metals in the electrolytecan be deposited in the negative electrode. The supplemental lithiumstabilizes the transition metals in the positive electrode activematerial such that the incorporation of the transition metals into theelectrolyte and correspondingly the negative electrode is reduced oreliminated. Thus, in some embodiments, after 500 charge/discharge cyclesof battery between 4.5V and 2 V, the negative electrode comprises nomore than about 5 weight percent transition metals, in furtherembodiments no more than about 2.5 weight percent, in additionalembodiments no more than about 2 weight percent and in other embodimentsno more than about 1 weight percent transition metals in the negativeelectrode. A person of ordinary skill in the art will recognize thatadditional ranges of transition metal concentrations within the explicitranges above are contemplated and are within the present disclosure.

Differential scanning calorimetry measurements suggest that theinitially formed SEI layer is more stable if supplemental lithium ispresent. In particular, if the anode material is removed after aformation charge step, the negative electrode active material does nothave a rise in heat flow above baseline heat capacity below 110° C. ifsupplemental lithium is present. If the SEI layer is formed with thelithium rich negative electrode active material and no supplementallithium, a rise in heat flow has been observed as low as about 100° C.If the SEI layer is formed by electrochemical lithiation of the negativeelectrode active material separate from the cathode active material, theSEI layer has been found to be particularly stable with stabilityobserved to above 130° C.

Battery Properties

Batteries formed from lithium rich positive electrode active materialsand supplemental lithium have demonstrated desirable performance underrealistic discharge conditions. Specifically, the active materials havedemonstrated a high specific capacity upon cycling of the batteries atmoderate discharge rates. In particular, the initial specific capacityof the positive electrode active material is approximately unchangedwhen supplemental lithium is included. The irreversible capacity loss onthe first cycle decreases. Also, the specific capacity on cyclingsignificantly improves with inclusion of supplemental lithium.

As noted above, the irreversible capacity loss is the difference betweenthe first charge specific capacity and the first discharge specificcapacity. With respect to the values described herein, the irreversiblecapacity loss is in the context of the positive electrode activematerials, which is evaluated relative to a lithium metal negativeelectrode. In some embodiments, the irreversible capacity loss is nomore than about 30 mAh/g, in further embodiments no more than about 25mAh/g, and in other embodiments no more than about 15 mAh/g. A person ofordinary skill in the art will recognize that additional ranges ofirreversible capacity loss are contemplated and are within the presentdisclosure.

In general, various similar testing procedures can be used to evaluatethe capacity performance of the battery positive electrode materials.Suitable testing procedures are described in more detail in the examplesbelow. Specifically, the battery can be cycled between 4.5 volts and 2volts at room temperature, although other ranges can be used withcorrespondingly different results, and the first cycle is charged anddischarged at a rate of C/10, the second and third cycles have acharge/discharge rate of C/5 and subsequent cycling is at a rate of C/3unless specified otherwise with charging at C/3. As noted above, thespecific discharge capacity is very dependent on the discharge rate.Again, the notation C/x implies that the battery is discharged at a rateto fully discharge the battery to the selected voltage minimum in xhours.

In some embodiments, the initial specific capacity is significantlydependent on the composition of the lithium rich positive electrodeactive material. Based on the inclusion of the supplemental lithium, thefade of the specific capacity is dramatically reduced relative to acorresponding battery without the supplemental lithium. In someembodiments, the room temperature specific discharge capacity at the200th cycle from 4.5 volts to 2 volts is at least about 92.5% of the 5thcycle specific discharge capacity at a C/3 rate, and in furtherembodiments at the 400th cycle at least about 90% of the 5th cycledischarge capacity, cycled at a discharge rate of C/3. Also, thesupplemental lithium can be effective to reduce fade at higher rates.Specifically, the positive electrode active materials can have aspecific discharge capacity at the 175th cycle at least about 75% of 5thcycle specific capacity at a rate of 1 C discharged from 4.5V to 2.0V atroom temperature, and in further embodiments at least about 85% of the5th cycle specific capacity at a rate of 1 C discharged from 4.5 voltsto 2 volts at room temperature. Good cycling has also been found at 55°C. Specifically, the specific capacity of the positive electrode activematerial at the 45th cycle can be at least about 90% and in furtherembodiments at least about 95% of the 5th cycle specific dischargecapacity when discharged from the 5th cycle to the 45th cycle at a C/3rate at a temperature of 55° C. A person of ordinary skill in the artwill recognize that additional ranges of specific capacity arecontemplated and are within the present disclosure.

The results below demonstrate the growth of discharge capacity in avoltage range from 2.5V to 3V. When supplemental lithium is present thecapacity from this voltage range is relatively stable with cycling,while without supplemental lithium this contribution to the capacitydiminishes relatively quickly with cycling. In some embodiments, fromabout 300 cycles to about 600 cycles the positive electrode activematerial has a specific discharge capacity of at least about 90 mAh/gbetween 3V and 2.5V, in other embodiments at least about 100 mAh/g andin further embodiments at least about 105 mAh/g. A person of ordinaryskill in the art will recognize that additional ranges of dischargecapacity within the explicit ranges above are contemplated and arewithin the present disclosure.

EXAMPLES Example 1 Synthesis of Cathode Active Material

This example demonstrates the formation of a desired positive electrodeactive material using a carbonate or hydroxide co-precipitation process.

Stoichiometric amounts of metal precursors were dissolved in distilledwater to form an aqueous solution with the metal salts in the desiredmolar ratios. Separately, an aqueous solution containing Na₂CO₃ and/orNH₄OH was prepared. For the formation of the samples, one or bothsolutions were gradually added to a reaction vessel to form metalcarbonate or hydroxide precipitates. The reaction mixture was stirred,and the temperature of the reaction mixture was kept between roomtemperature and 80° C. The pH of the reaction mixture was in the rangefrom 6-12. In general, the aqueous transition metal solution had aconcentration from 1M to 3M, and the aqueous Na₂CO₃/NH₄OH solution had aNa₂CO₃ concentration of 1M to 4M and/or a NH₄OH concentration of 0.2-2M.The metal carbonate or hydroxide precipitate was filtered, washedmultiple times with distilled water, and dried at 110° C. for about 16hrs to form a metal carbonate or hydroxide powder. Specific ranges ofreaction conditions for the preparation of the samples are furtheroutlined in Table 1, where the solution may not include both Na₂CO₃ andNH₄OH.

TABLE 1 Reaction Process Condition Values Reaction pH 6.0-12.0 Reactiontime 0.1-24 hr Reactor type Batch Reactor agitation speed 200-1400 rpmReaction temperature RT-80° C. Concentration of the metal salts 1-3MConcentration of Na₂CO₃ 1-4M Concentration of NH₄OH 0.2-2M Flow rate ofthe metal salts 1-100 mL/min Flow rate of Na₂CO₃ & NH₄OH 1-100 mL/min

An appropriate amount of Li₂CO₃ or LiOH powder was combined with thedried metal carbonate or hydroxide powder and thoroughly mixed with aJar Mill, double planetary mixer, or dry powder rotary mixer to form ahomogenous powder mixture. A portion, e.g. 5 grams, of the homogenizedpowders was calcined in a step to form the oxide, followed by anadditional mixing step to further homogenize the powder. The furtherhomogenized powder was again calcined to form the highly crystallinelithium composite oxide. Specific ranges of calcination conditions arefurther outlined in Table 2 (scfh is a standard cubic foot per hour).

TABLE 2 Calcination Process Condition Values 1^(st) Step Temperature400-800° C. Time 1-24 hr protective gas Nitrogen or Air Flow rate ofprotective gas 0-50 scfh 2^(nd) Step Temperature 700-1100° C. Time 1-36hr protective gas Nitrogen or Air Flow rate of protective gas 0-50 scfh

The positive electrode composite material particles thus formedgenerally have a substantially spherical shape and are relativelyhomogenous in size. The product composition was assumed to correspond tothe portions of the metal reactants used to fowl the composition withthe oxygen adjusting to yield the overall targeted oxidation state. Theoverall formula for these compositions can be written as x Li₂MnO₃.(1−x)Li Ni_(u)Mn_(v)Co_(w)O₂ (formula I) or Li_(1+b)Ni_(α)Co_(γ)Mn_(β)O₂(formula II). In the following examples, positive electrode activematerials are use that correspond with X=0.3 with 51.90 mole percentmanganese or X=0.5 with 65.63 mole percent manganese.

Example 2 Formation of Metal Fluoride Coated Positive ElectrodeMaterials

As described in this example, a portion of the lithium metal oxide (LMO)composition synthesized as described in Example 1 were coated with athin layer of either aluminum fluoride (AlF₃) or magnesium fluoride(MgF₂). With respect to aluminum fluoride coatings, for a selectedamount of aluminum fluoride, an appropriate amount of saturated solutionof aluminum nitrate was prepared in an aqueous solvent. The lithiummetal oxide particles were then added into the aluminum nitrate solutionto form a mixture. The mixture was mixed vigorously for a period of timeto homogenize. The length of mixing depends on the volume of themixture. After homogenization, a stoichiometric amount of ammoniumfluoride was added to the homogenized mixture to form aluminum fluorideprecipitate while retaining the source of fluorine. Upon the completionof the precipitation, the mixture was stirred at 80° C. for 5 h. Themixture was then filtered and the solid obtained was washed repeatedlyto remove any un-reacted materials. The solid was calcined in nitrogenatmosphere at 400° C. for 5 h to form the AlF₃ coated lithium metaloxide material. Different thicknesses of AlF₃ below 25 nm have been usedfor these studies.

Samples of lithium metal oxide (LMO) particles synthesized as describedin Example 1 were coated with 0.5 mole percent MgF₂. A stoichiometricamount of the magnesium nitrate was dissolved in water and mixed withthe corresponding amount of the lithium metal oxide under constantstirring. Then, ammonium fluoride was added to the mixture slowly whilecontinuing the stirring. After the addition of an excess of ammoniumfluoride, the mixture was heated to about 80° C. for about 5 hours.After the deposition was completed, the mixture was filtered andcalcined at 450° C. for 5 hours under a nitrogen atmosphere.Characterization of lithium rich LMO particles with an MgF₂ coatingusing x-ray diffraction and transmission electron microscopy isdescribed in the '226 application. Generally, the positive electrodeparticles included nanocoating thicknesses less 25 nm

Example 3 Battery Formation

This example describes the formation of coin cell batteries comprising apositive electrode comprising lithium metal oxide (LMO) and a negativeelectrode comprising graphitic carbon.

A positive electrode was formed from LMO oxide powders. Lithium metaloxide powders were synthesized as described in Example 2. The LMOpowders were mixed thoroughly with acetylene black (Super P™ fromTimcal, Ltd, Switzerland) and graphite (KS 6™ from Timcal, Ltd) to forma homogeneous powder mixture. Separately, Polyvinylidene fluoride PVDF(KF1300™ from Kureha Corp., Japan) was mixed with N-methyl-pyrrolidone(Sigma-Aldrich) and stirred overnight to form a PVDF-NMP solution. Thehomogeneous powder mixture was then added to the PVDF-NMP solution andmixed for about 2 hours to form homogeneous slurry. The slurry wasapplied onto an aluminum foil current collector to form a thin wet filmand a positive electrode material was formed by drying the laminatedcurrent collector in a vacuum oven at 110° C. for about two hours toremove NMP. The positive electrode material was pressed between rollersof a sheet mill to obtain a positive electrode with desired thickness.The dried electrode comprised at least about 75 weight percent activemetal oxide, at least about 3 weight percent acetylene black, at leastabout 1 weight percent graphite, and at least about 2 weight percentpolymer binder.

A negative electrode was formed from graphitic carbon. The negativeelectrode comprised at least about 75 weight percent graphite and atleast about 1 weight percent acetylene black with the remaining portionof the negative electrode being polymer binder. The acetylene black wasinitially mixed with NMP solvent to form a uniform dispersion. Thegraphite and polymer were added to the dispersion to form a slurry. Theslurry was applied to a copper foil to form the negative electrode afterdrying.

In some examples below, a battery with supplemental lithium was formed.Supplemental lithium was provided to the battery eitherelectrochemically or by direct addition of lithium metal to the negativeelectrode. Electrochemical addition of supplemental lithium comprisedintercalating lithium into the negative electrode prior to ultimatebattery formation. In particular, a lithiation coin cell was formedcomprising a graphitic carbon electrode as described above, an electrodeformed from lithium foil, and a separator disposed between the graphiticcarbon electrode and the lithium foil electrode. The lithiation coincell was cycled three times. Each cycle comprised intercalation oflithium into the graphite to 5 mV and a de-intercalation to 1.5 V, withan initial open circuit voltage of about 3V. In this configuration, thegraphitic carbon electrode acted as the positive electrode and thelithium electrode acted as the negative electrode. After the finalde-intercalation, the lithiation cell was partially intercalated toobtain a desired percentage lithiation of the graphitic carbonelectrode. The desired percentage lithiation was determined based uponthe discharge (de-intercalation/de-alloying) capacity of the graphiticcarbon electrode and the measured amount of intercalation during thefinal partial charge. After partial lithiation, the graphitic carbonelectrode was removed from the lithiation coin cell and an ultimate coincell battery was formed as described below using the partially lithiatedgraphitic carbon electrode as the negative electrode.

Alternatively, direct addition of lithium metal comprised addingelemental lithium powder to the negative electrode prior to coin cellbattery formation. In a first approach, a desired amount of stabilizedlithium metal powder SLMP® (FMC Corp.) (stabilized lithium metal powder)was loaded into a vial and the vial was then capped with a meshcomprising nylon or stainless steel with a mesh size between about 40 μmto about 80 μm. SLMP® (FMC corp.) was then deposited onto the negativeelectrode by shaking or tapping the loaded vial over the negativeelectrode. In other embodiments, a slurry was formed by suspending afine powder of SLMP® in p-xylene. The slurry was then applied to theformed negative electrode, and the coated negative electrode was dried.For either approach of adding the lithium powder to the negativeelectrode, the coated negative electrode was then compressed to ensuremechanical stability.

The amount of added lithium (“supplemental lithium”) was expressedrelative to the intercalation capacity of the negative electrode. Inparticular, assuming a lithium intercalation reaction at the negativeelectrode described by Li+C₆→LiC₆, the percent excess lithium wasexpressed by the formula

${\% \mspace{14mu} {Lithiation}} = {\frac{{wt}_{Li}}{{\left( \frac{\mathcal{M}_{{LiC}_{6}}}{\mathcal{M}_{C_{6}}} \right) \times {wt}_{active}} - {wt}_{active}} \times 100}$

where wt_(Li) is the weight of lithium applied to the negativeelectrode, M_(LiC) ₆ is the molecular weight of LiC₆, M_(C) ₆ is themolecular weight of C₆, and wt_(active) is the weight of the activenegative electrode material in the negative electrode.

Generally, the negative electrode was formed to give a load balancing ofabout 107% relative to the positive electrode, unless otherwise noted.The load balancing was determined by the ratio of the theoreticalcapacity per area of the negative electrode to the theoretical capacityper area of the positive electrode which can be written as

$\frac{z \times \left\lbrack {{a\left( {1 - \frac{\% \mspace{14mu} {Lithiation}}{100}} \right)} \times b} \right\rbrack}{y \times \left( {c \times d} \right)}$

where a and b are the weight and theoretical specific capacity of theactive negative electrode material, respectively, y is the area of thenegative electrode, c and d are the weight and theoretical specificcapacity of the active positive electrode material, respectively, and zis the area of the positive electrode. The theoretical capacity of thepositive electrode active material is calculated based on fullextraction of all of the initial lithium.

To form a coin cell battery, the positive electrode and negativeelectrode were placed inside an argon filled glove box. An electrolytewas selected to be stable at high voltages, and appropriate electrolytesare described in the '992 application. A trilayer(polypropylene/polyethylene/polypropylene) micro-porous separator (2320from Celgard, LLC, NC, USA) soaked with electrolyte was placed betweenthe positive electrode and the negative electrode. A few additionaldrops of electrolyte were added between the electrodes. The electrodeswere then sealed inside a 2032 coin cell hardware (Hohsen Corp., Japan)using a crimping process to form a coin cell battery. The coin cellbatteries were tested with a Maccor cycle tester and the results aredescribed in the following examples. Additionally, unless otherwisenoted, performance data was obtained at room temperature. Additionally,unless otherwise noted, the batteries were charged and dischargedbetween 4.5V and 2V at a rate of C/10 over the first cycle and at a rateof C/3 for subsequent cycles.

Example 4 Battery Performance: Long Cycling with Lithiation UsingElemental Lithium

This example demonstrates the long cycling performance of coin cellbatteries formed with excess lithium added to the negative electrodeelectrochemically.

To demonstrate long term cycling performance, coin cell batteries werefabricated and cycled. The coin cell batteries were fabricated asdescribed in Example 3 and varied in positive electrode composition,excess lithium, and load balancing as indicated below. In particular,batteries used in this example comprised positive electrodes formed fromnanocoated LMO wherein X=0.5 or X=0.3.

Cycling and Capacity

Batteries with supplemental lithium were seen to have improved cyclingperformance at moderate discharge rates over varied positive electrodecompositions. FIGS. 8 and 9 are plots comparing cycling performancebetween 4.5V and 2V of batteries with or without supplemental lithium ata charge/discharge rate of C/3 for cathode active materials with X=0.5(FIG. 8) and X=0.3 (FIG. 9). The first cycle charge and discharge rateswere C/10. In both FIGS. 8 and 9, negative electrodes with supplementallithium were formed with 30% supplemental lithium. With respect to FIG.8, the battery with supplemental lithium experienced a specific capacityloss of 20% over about 720 cycles while the same capacity loss wasobserved in the battery without supplemental lithium over about 180cycles. Similarly, with respect to FIG. 9, over 260 cycles, the batterywith supplemental lithium experienced a capacity loss of less than 1%while the battery without supplemental lithium experienced a capacityloss of 19% of the same number of cycles.

Batteries with supplemental lithium also had improved cyclingperformance at higher discharge rates and at higher temperatures. Forthe evaluation of batteries at rates of 1 C, batteries were formed with30% supplemental lithium. FIG. 10 is a plot comparing cyclingperformance of battery with or without supplemental lithium at a cyclingdischarge rate of 1 C. Over 180 cycles, the battery without supplementallithium showed significantly increased capacity fade relative to thebattery with the supplemental lithium. Equivalent batteries were formedto evaluate the performance at higher temperatures. FIG. 11 is a plotcomparing the cycling performance of batteries with or withoutsupplemental lithium cycled at a temperature of 55° C. Over 50 cycles,the battery without supplemental lithium showed significantly increasedcapacity fade relative to the battery with supplemental lithium.

Capacity and Voltage

While batteries with supplemental lithium maintained their capacityextremely well over relatively high numbers of cycles. FIG. 12 is a plotof discharge curves with voltage as a function of capacity for batterieswith or without supplemental lithium at four selected cycles. Thenegative electrode of the battery with supplemental lithium was formedwith 30% supplemental lithium. Discharge curves were obtained for bothbatteries during cycle number 10, 50, 300, and 500. Table 3 belowincludes the accumulated discharge capacities obtained over variousvoltage ranges for the discharge curves shown in FIG. 12. Generally, forboth of the batteries with or without supplemental lithium, thedischarge capacity decreased monotonically over a voltage range of4.0V-3.5V with cycling. On the other hand, the discharge capacity forboth the batteries with or without supplemental lithium increasedmonotonically over a voltage range of 3.0V-2.5V with cycling. A slowerdecay with cycling of the capacity with a small plateau or smallincrease at lower cycling is observed in the voltage range of 3.5V-3.0V.From the discharge curves in FIG. 12, it is observed that the batterywithout supplemental lithium undergoes a significant drop in capacitywith cycling over 500 cycles while the battery with the supplementallithium undergoes a very small drop in capacity.

TABLE 3 Capacity Capacity Capacity Negative 4.0 V-3.5 V 3.5 V-3.0 V 3.0V-2.5 V Cycles Electrode (mAh) (mAh) (mAh) 10 Lithiated 85 70 40Non-Lithiated 65 70 50 100 Lithiated 60 80 60 Non-Lithiated 45 70 45 300Lithiated 40 50 120 Non-Lithiated 22 45 85 500 Lithiated 35 45 130Non-Lithiated 12 40 70

Example 5 Battery Performance: Effect of Amount of Supplemental Lithiumby Direct Addition of Lithium Metal and Effect of Balancing of NegativeElectrode and Positive Electrode During Long Cycling

This example demonstrates the effect of load balancing and amount ofsupplemental lithium introduced by direct addition of lithium metalpowder on the long cycling performance of coin cell batteries.

To demonstrate performance with a large number of cycles, coin cellbatteries were fabricated and cycled. The coin cell batteries were asdescribed in Example 3 and were fabricated from positive electrodescomprising nanocoated LMO with X=0.5. The batteries varied in loadbalancing and supplemental lithium. In particular, batteries were loadbalanced at 107% or 120%. Additionally, batteries were formed with andwithout supplemental lithium added as an SLMP® lithium powder (FMCCorp.). Batteries formed with supplemental lithium comprised 5%, 30%, or50% supplemental lithium.

Generally, at both 107% and 120% load balancing, batteries withsupplemental lithium had improved cycling performance. FIGS. 13 and 14are plots comparing the cycling performance of batteries balanced at107% and 120%, respectively, for batteries with and without supplementallithium. With respect to FIG. 13, the battery with 5% supplementallithium had comparable cycling performance to the battery withoutsupplemental lithium. On the other hand, the batteries with 30% and 50%supplemental lithium significantly outperformed the battery withoutsupplemental lithium with a low amount of capacity fade out to 200cycles.

With respect to FIG. 14, specific discharge capacity as a function ofcycling is shown for batteries with supplemental lithium and a balanceof 120% anode capacity. With this negative electrode balance, thebatteries comprising 5%, 30%, and 50% supplemental lithium hadsignificantly improved cycling performance relative to the batterywithout supplemental lithium. The plot for the battery withoutsupplemental lithium is obtained with a balance of 107% anode capacity,but the results with 120% anode capacity and no supplemental lithium areexpected to be similar. For higher amounts of lithiation, the anodebalance did not significant alter the cycling performance.

Example 6 Battery Performance: Effect of Amount of Supplemental Lithiumby Electrochemical Addition of Lithium and Effect of Balancing ofNegative Electrode and Positive Electrode During Long Cycling

This example demonstrates the long term cycling performance of coin cellbatteries formed with supplemental lithium introduced by electrochemicallithiation. The batteries used in this example were formed as describedin Example 3. In particular, batteries comprised positive electrodesfabricated from nanocoated LMO wherein x=0.5. Batteries were formed withand without supplemental lithium added electrochemically.

Generally, batteries with initially electrochemically lithiated negativeelectrodes showed superior long term cycling performance relative tobatteries with no supplemental lithium. Batteries were formed witheither 5%, 15%, 30%, or 50% supplemental lithium added to the negativeelectrode electrochemically. Batteries were selectively balanced with arelative negative electrode capacity at 106%, 120%, or 140%, and thebatteries were cycled 150 times. FIG. 15 is a histogram of specificcapacities for the various batteries obtained at the 4th and 150thdischarge cycles when cycled from 4.5V to 2 V. The results at the 150thcycle are plotted with a dark shading while the result at the 1st cycleare plotted in a light shading superimposed over the 150 cycle results.It was generally seen that the inclusion of supplemental lithiumincreased initial battery capacity, although some of the larger loadingsof supplemental lithium resulted in a relatively small decrease ininitial capacity. However, the batteries with supplemental lithiumexhibit decreased capacity fade relative to the battery without thesupplemental lithium.

Example 7 Effect of Supplemental Lithium on Positive and NegativeElectrodes

This example demonstrates the effects of supplemental lithium on thepositive and negative electrodes of coin cell batteries upon cycling.

Batteries used in this Example were formed as described in Example 3 andcomprised positive electrodes formed from nanocoated LMO where X=0.5.Batteries were formed either without supplemental lithium or with 5%supplemental lithium supplied as SLMP® lithium powder supplied on thesurface of the negative electrode. The negative electrode was balancedat 107%. The batteries were charged and discharged over the first cycleat a rate of C/10, over the second and third cycles at a rate of C/5,and over subsequent cycles at a rate of C/3. Unless otherwise noted, thebattery compositions and cycling parameters just described were used toobtain the data below in this example.

Negative Electrode Stability

The effect of supplemental lithium on the negative electrode wasinitially characterized by determining the amount of excess lithiumpresent in a battery after cycling. In particular, it was seen that evenat large cycle numbers, excess lithium was still present in dischargedbatteries and that batteries with supplemental lithium had significantlygreater amounts of excess lithium relative to batteries withoutsupplemental lithium. Ten coin cell batteries were formed: 7 batterieswith supplemental lithium and 3 batteries without supplemental lithium.Each battery was cycled a predetermined number of times ranging from0-1000. After cycling, each battery was discharged to 2 V, and thenegative electrode was removed. Coin cell batteries were subsequentlyformed by assembling the removed negative electrode from each batteryand placed across a separator from a lithium foil electrode. Eachtesting coin cell was then charged a single time to extract lithium fromthe graphitic carbon electrode. FIG. 16 is a plot of voltage vs.capacity for test coin-cells charged to 1.5 V during lithium extraction.The results reveal a substantially greater amount of lithium in thenegative electrodes recovered from cycled batteries with supplementallithium relative to the negative electrodes recovered from the cycledbatteries without supplemental. In particular, the recovered negativeelectrode with supplemental lithium that was cycled 550 times had asignificantly greater amount of lithium relative to the recoverednegative electrode without supplemental lithium that was cycled only 5times. At 1000 cycles, the battery with supplemental lithium wasessentially depleted of supplemental lithium since the negativeelectrode exhibited a low remaining capacity.

Furthermore, the inclusion of supplemental lithium was seen to increasethe stability of the solid electrolyte interface (SEI) layer fixated ona graphitic electrode. Three negative electrodes were prepared. A firstnegative electrode was prepared as described in Example 3 by initiallyforming a battery with 30% supplemental lithium added electrochemicallyand a positive electrode comprising nanocoated LMO with x=0.5. Thebattery with supplemental lithium was cycled 30 times, and the negativeelectrode was charged to 4.5V and removed. A second negative electrodewas prepared by initially forming a battery without supplemental lithiumas described in Example 3 wherein the positive electrode comprisednanocoated LMO with X=0.5. The battery without supplemental lithium wascharged to 4.5V, and the negative electrode was removed. A thirdnegative electrode was prepared by initially forming a lithiation cellas described in Example 3 comprising a graphitic electrode, a lithiumfoil electrode, and a separator disposed between the electrodes. Thelithiation cell was then cycled three times and then discharged to 5 mVto electrochemically lithiate the graphitic electrode. The lithiatednegative electrode was subsequently removed from the lithiation cell.FIG. 17 is a plot showing the results of differential scanningcalorimetry (“DSC”) analysis performed on the three negative electrodes.Relative to the second negative electrode, the first negative electrodeshowed greater stability at higher temperatures. The second negativeelectrode exhibited an increase in heat flow relative to the heating ofthe material at a temperature between about 90 and 100° C. while thefirst negative electrode exhibited an increase in heat flow between 120and 130° C. Additionally, relative to both the second and thirdelectrodes, the first electrode showed significantly more stability withan increase in heat flow not observed until about 150° C., whichsuggests a more stable SEI layer until relatively high temperatures.

Positive Electrode Stability

The effect of supplemental lithium on the positive electrode wascharacterized in part by analyzing its effect on the structure of thepositive electrode. The formation step for the battery withoutsupplemental lithium comprised a two-step formation process consistingof an initial charge to 4.2V, resting the battery in an open circuit for7 days, and then charging the battery to 4.6V. A two step formationprocess is described further in copending U.S. patent application Ser.No. 12/732,520 to Amiruddin et al., entitled “High Voltage BatteryFormation Protocols and Control of Charging and Discharging forDesirable Long Term Cycling Performance,” incorporated herein byreference. The battery with supplemental lithium was charged anddischarged in the first cycle at a rate of C/10. Both batteries werecycled 550 times at a charge and discharge rate of C/3 between 4.5V and2V and subsequently dismantled. The positive electrode of each batterywas analyzed using high resolution transmission electron microscopy(“TEM”). FIGS. 18 and 19 are TEM images of the positive electrodematerial obtained from the cycled coin cell batteries withoutsupplemental lithium (FIG. 18) and with supplemental lithium (FIG. 19).FIG. 18 reveals that after cycling, the positive electrode obtained fromthe battery without supplemental underwent structural changes to adisordered structure and with some evidence of porosity consistent withdissolution of material from the particles. On the other hand, thepositive electrode obtained from the battery with supplemental lithiumreveals a highly ordered structure after cycling, as indicated in FIG.19, which is consistent with little if any dissolution of material fromthe particle. These results are consistent with electron diffractionresults shown in FIG. 20, which is a composite of diffraction patternsobtained from electron diffraction spectroscopy measurements aftercycling of the positive electrode materials without supplemental lithium(left panel) and with supplemental lithium (right panel). The x-raydiffraction pattern for the materials with supplemental lithium show avery ordered pattern consistent with a highly crystalline structure,while the x-ray diffraction pattern of the material without supplementallithium exhibits a pattern consistent with low structural order.

Compositional analysis reveals that structural changes in the positiveelectrode during cycling are accompanied by changes in chemicalcomposition. After cycling the batteries with and without supplementallithium for 550 cycles, the chemical composition of the positiveelectrodes and the negative electrodes was analyzed. Specifically,samples were taken from the positive electrodes and analyzed usingenergy dispersive x-rays (“EDS”). EDS results for the positiveelectrodes are shown in Table 4.

TABLE 4 From Battery From Battery W/O Supplemental W/ SupplementalLithium Lithium Element Weight % Atomic % Weight % Atomic % Mn 33.818.49 43.12 22.62 Co 9.48 5.29 8.1 3.96 Ni 14.75 9.86 11.03 5.41 O 41.9763.92 37.75 68.01EDS analysis show that dissolution of Mn from the positive electrode isreduced in the battery with supplemental lithium. Results ofglow-discharge mass spectrometry (“GDMS”) analysis of the negativeelectrodes recovered from the batteries with and without supplementallithium are shown in Table 5.

TABLE 5 From Battery W/O From Battery W/ Element Supplemental LithiumSupplemental Lithium Mn 8.6 wt % 0.12 wt % Co   2 wt %  85 (ppm) Ni 2.7wt % 360 (ppm)GDMS analysis shows a much lesser concentration of Mn, Co, and Ni in thenegative electrode obtained from the battery with the supplementallithium. For the batteries without supplemental lithium, large amountsof manganese is found in the negative electrode and less but stillsubstantial amounts of cobalt and nickel are also found in the negativeelectrode.

Analysis of differential capacity measurements during battery cyclingwas used to determine the effect of the above mentioned compositionalchanges on battery performance. Batteries with supplemental lithium andwithout supplemental lithium were cycled 400 times. FIG. 21 is a plotshowing differential capacity for charging (positive values) anddischarging (negative values) for the battery without supplementallithium over the first 300 cycles. The inset of FIG. 21 is anenlargement of the peak present at about 3.05V-3.25V seen in thedifferential capacity during charging. It was seen that 2.5V-3Vdischarge activity increased over the first 300 cycles while 3.25V-4Vdischarge activity decreased over the same number of cycles. FIG. 22 isa plot showing differential capacity plots for both batteries generatedat the 300^(th) and 400^(th) cycles. During discharge, the battery withsupplemental lithium was seen to have increased 2.5V-3V activityrelative to the battery without supplemental lithium. Additionally, thebattery with supplemental lithium was seen to have increased 3.25-4Vactivity relative to the battery without supplemental lithium duringdischarge. Furthermore, FIG. 22 shows that with respect to 2.5V-3Vactivity during discharge, the battery comprising supplemental lithiumhad a smaller difference in the differential discharge capacity betweenthe 300th and 400th cycles, relative to the battery without supplementallithium. These results suggested that supplemental lithium furtherstabilizes the positive electrode of corresponding batteries.

Furthermore, the improved cycling performance of lithiated batteriesdemonstrated in Example 4 above can be at least partially explained bythe stabilization of the positive electrode due to the presence ofexcess lithium. Batteries with and without supplemental lithium werecycled 500 and 600 times, respectively. FIG. 23 is a plot showing theeffect of ionic activity in the positive electrode on dischargecapacity.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. In addition, although thepresent invention has been described with reference to particularembodiments, those skilled in the art will recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention. Any incorporation by reference of documents above islimited such that no subject matter is incorporated that is contrary tothe explicit disclosure herein.

1-14. (canceled)
 15. A lithium ion battery comprising: a negativeelectrode comprising a lithium intercalation composition; a positiveelectrode comprising Li_(1+x)M_(1−y)O_(2−z)F_(z) where M is one or moremetal elements, x is from about 0.01 to about 0.33, y is from aboutx−0.2 to about x+0.2 with the proviso that y≧0, and z is from 0 to about0.2; and a separator between the negative electrode and the positiveelectrode, wherein after 600 cycles between 4.5V and 2.0V the negativeelectrode comprises no more than about 1 weight percent transitionmetals from the positive electrode.
 16. The lithium ion battery of claim15 wherein after 600 cycles, the negative electrode comprises no morethan about 0.25 weight percent transition metals from the positiveelectrode.
 17. A lithium ion battery comprising a positive electrode, anegative electrode, a separator between the positive electrode and thenegative electrode and an electrolyte comprising lithium ions, thenegative electrode comprising a lithium intercalation/alloyingcomposition, wherein the positive electrode comprises a compositionapproximately represented by a formula Li_(1+x)M_(1−y)O_(2−z)F_(z) whereM is one or more metal elements, x is from about 0.01 to about 0.33, yis from about x−0.2 to about x+0.2 with the proviso that y≧0, and z isfrom 0 to about 0.2 and wherein after cycling the battery for 20 cyclesfrom 4.5 volts to 2 volts and after discharging the battery to 98% ofthe discharge capacity, the negative electrode can be removed andelectrochemically de-intercalated/de-alloyed with a capacity of at leastabout 0.5% of the negative electrode capacity with the correspondingremoval of lithium from the negative electrode.
 18. The lithium ionbattery of claim 17 wherein after cycling the battery for 20 cycles from4.5 volts to 2 volts and after discharging the battery to 98 percent ofcapacity, the negative electrode can be removed and electrochemicallyde-intercalated/de-alloyed with a capacity of at least about 2.5% of thenegative electrode capacity with the corresponding removal of lithiumfrom the negative electrode.
 19. The lithium ion battery of claim 17wherein after cycling the battery for 550 cycles from 4.5 volts to 2volts and after discharging the battery to 98 percent of capacity, thenegative electrode can be removed and electrochemicallyde-intercalated/de-alloyed with a capacity of at least about 0.5% of thenegative electrode capacity with the corresponding removal of lithiumfrom the negative electrode.
 20. A lithium ion battery comprising apositive electrode, a negative electrode, a separator between thepositive electrode and the negative electrode and an electrolytecomprising lithium ions, the negative electrode comprising a lithiumintercalation/alloying composition, wherein the positive electrode has aroom temperature specific discharge capacity at the 200th cycle that isat least about 92.5% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 200th cycle at a C/3 rate from 4.5Vto 2V.
 21. The lithium ion battery of claim 20 wherein the positiveelectrode has a room temperature specific discharge capacity at the400th cycle that is at least about 90% of the 5th cycle specificdischarge capacity when discharged from the 5th cycle to the 400th cycleat a C/3 rate.
 22. The lithium ion battery of claim 20 furthercomprising supplemental lithium.
 23. A lithium ion battery comprising apositive electrode, a negative electrode, a separator between thepositive electrode and the negative electrode and an electrolytecomprising lithium ions, the negative electrode comprising a lithiumintercalation/alloying composition, wherein the battery has a roomtemperature specific discharge capacity at the 175th cycle that is atleast about 75% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 175th cycle at a 1 C rate from 4.5Vto 2V.
 24. The lithium ion battery of claim 23 wherein the battery has aroom temperature specific discharge capacity at the 175th cycle that isat least about 85% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 175th cycle at a 1 C rate from 4.5Vto 2V.
 25. The lithium ion battery of claim 23 further comprisingsupplemental lithium.
 26. A lithium ion battery comprising a positiveelectrode, a negative electrode, a separator between the positiveelectrode and the negative electrode and an electrolyte comprisinglithium ions, the negative electrode comprising a lithiumintercalation/alloying composition, wherein the battery has a specificdischarge capacity at the 45th cycle that is at least about 90% of the5th cycle specific discharge capacity when discharged from the 5th cycleto the 45th cycle at a C/3 rate at a temperature of 55° C. from 4.5V to2V.
 27. The lithium ion battery of claim 26 wherein the battery has aspecific discharge capacity of at least about 260 in mAh/g at the 5thcycle and a specific discharge capacity at the 45th cycle that is atleast about 95% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 45th cycle at a C/3 rate at atemperature of 55° C. from 4.5V to 2V. 28.-34. (canceled)
 35. A lithiumion battery comprising: a negative electrode comprising a lithiumintercalation composition; a positive electrode comprisingLi_(1+x)M_(1−y)O_(2−z)F_(z) where M is one or more metal elements, x isfrom about 0.01 to about 0.33, y is from about x−0.2 to about x+0.2 withthe proviso that y≧0, and z is from 0 to about 0.2; and a separatorbetween the negative electrode and the positive electrode, wherein fromabout 300 cycles to about 600 cycles the positive electrode activematerial has a specific discharge capacity of at least about 90 mAh/gbetween 3V and 2.5V.
 36. The lithium ion battery of claim 15 wherein thenegative electrode comprises graphitic carbon.
 37. The lithium ionbattery of claim 15 wherein the positive electrode comprises lithiummetal oxide that can be approximately represented by a formulaLi_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O₂, where b ranges from about 0.05 toabout 0.3, α ranges from 0 to about 0.4, β range from about 0.2 to about0.65, γ ranges from 0 to about 0.46, and δ ranges from about 0 to about0.15, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca, Ce, Y,Nb, Cr, Fe, V, Li, or combinations thereof.
 38. The lithium ion batteryof claim 15 wherein the positive electrode comprises lithium metal oxidethat can be approximately represented by a formula of xLi₂MnO₃.(1−x)LiMO₂, where M represents one or more metal ions having an averagevalance of +3, and 0<x<1.
 39. The lithium ion battery of claim 15wherein after cycling the battery for 20 cycles from 4.5 volts to 2.0volts and after fully discharging the battery to 2.0 volts, the negativeelectrode can be removed and discharged with a specific capacity of atleast about 1 mAh/g with the corresponding removal of lithium from thenegative electrode.
 40. The lithium ion battery of claim 15 wherein thepositive electrode has a room temperature specific discharge capacity atthe 200th cycle that is at least about 92.5% of the 5th cycle specificdischarge capacity when discharged from the 5th cycle to the 200th cycleat a C/3 rate.
 41. The lithium ion battery of claim 15 furthercomprising supplemental lithium.
 42. The lithium ion battery of claim 15wherein the negative electrode comprises silicon.
 43. The lithium ionbattery of claim 17 wherein after 600 cycles between 4.5V and 2.0V thenegative electrode comprises no more than about 1 weight percenttransition metals from the positive electrode.
 44. The lithium ionbattery of claim 17 wherein the positive electrode has a roomtemperature specific discharge capacity at the 200th cycle that is atleast about 92.5% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 200th cycle at a C/3 rate from 4.5Vto 2V.
 45. The lithium ion battery of claim 17 wherein the battery has aspecific discharge capacity at the 45th cycle that is at least about 90%of the 5th cycle specific discharge capacity when discharged from the5th cycle to the 45th cycle at a C/3 rate at a temperature of 55° C.from 4.5V to 2V.
 46. The lithium ion battery of claim 17 wherein fromabout 300 cycles to about 600 cycles the positive electrode activematerial has a specific discharge capacity of at least about 90 mAh/gbetween 3V and 2.5V.
 47. The lithium ion battery of claim 17 wherein thenegative electrode comprises graphitic carbon.
 48. The lithium ionbattery of claim 17 wherein the negative electrode comprises silicon.49. The lithium ion battery of claim 17 wherein the positive electrodecomprises lithium metal oxide that can be approximately represented by aformula Li_(1+b)Ni_(α)Mn_(β)Co_(γ)A_(δ)O₂, where b ranges from about0.05 to about 0.3, α ranges from 0 to about 0.4, β range from about 0.2to about 0.65, γ ranges from 0 to about 0.46, and δ ranges from about 0to about 0.15, and where A is Mg, Sr, Ba, Cd, Zn, Al, Ga, B, Zr, Ti, Ca,Ce, Y, Nb, Cr, Fe, V, Li, or combinations thereof.
 50. The lithium ionbattery of claim 17 further comprising supplemental lithium.
 51. Thelithium ion battery of claim 17 wherein the battery has a roomtemperature specific discharge capacity at the 175th cycle that is atleast about 75% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 175th cycle at a 1 C rate from 4.5Vto 2V.
 52. The lithium ion battery of claim 26 wherein the negativeelectrode comprises graphitic carbon.
 53. The lithium ion battery ofclaim 26 wherein the negative electrode comprises silicon.
 54. Thelithium ion battery of claim 26 wherein the positive electrode compriseslithium metal oxide that can be approximately represented by formulaLi_(1+x)M_(1−y)O_(2−z)F_(z) where M is one or more metal elements, x isfrom about 0.01 to about 0.33, y is from about x−0.2 to about x+0.2 withthe proviso that y≧0, and z is from 0 to about 0.2.
 55. The lithium ionbattery of claim 26 further comprising supplemental lithium.
 56. Thelithium ion battery of claim 26 wherein the battery has a roomtemperature specific discharge capacity at the 175th cycle that is atleast about 75% of the 5th cycle specific discharge capacity whendischarged from the 5th cycle to the 175th cycle at a 1 C rate from 4.5Vto 2V.